my backfiring problem...

I'm actually went the LS route on the 944, and plan to use the stock GM ECU that came with it. That said, I've followed the MS along the years and it's actually far more user friendly than it was a few product generations ago. I can remember a friend had one of the 1st gen megas controlling a VW project. Back then things were a lot clunkier, and the whole situation was week after week of headaches for him.

At this point the LTX/optispark Megasquirt trail has been blazed, and they sell megasquirt units that are near plug n' play for that application. I'm pretty sure Megasquirt 3 has USB for flashing, aannnnd downloading track log data! Not to mention 8 channel sequential injection support with an add-on card. Very straight-forward graphical user interface for editing your parameters. Multiple ways of viewing nearly everything, and sexy graphs for nerd pleasure. .. It goes on and on.

I've never put one into any of my cars, but I've dreamed of doing it for my Toyota daily drivers to clear up some irritating OEM ghosts from all the Frankenstein-ing that goes on in my herd. The only thing holding me back is that MS3 can't control the transmission that I'm working with (not supported... yet)

i guess i don't mind the hijack...lol

I won't drive it until i get it tuned, i'm really starting to worry that this damn this is gonna eat me alive. I'm losing a little bit of my drive to keep fixing it, because it's just not getting better! It seems like it gets worse every time i fix it actually.

I have a couple of questions:

1. Should i have my injectors cleaned and flow matched before tuning?
2. Should i replace lifters and pushrods before tuning?
3. Should i have the car tuned on the stock throttle body or the BBK 58mm one?
a. I'm leaning toward BBK on this question because it's newer and much nicer, but selling it might bring in some money for fixing other stuff...
4. Should i drop back down to my 3 inch intake tubing? The 4 inch stuff is rubbing on the hood a bit, but i don't know if i can use the 3's after having the 4 stuffed into the intake elbow.
5. Should i pull all the $#** out, part the motor, and buy a LS1?

edit: oh and what's an AR gauge? do you mean an Air-Fuel Ratio Gauge?
edit #2: sbwrench, i haven't noticed ANY change because of weather, it did this same kind of hesitation when it had a cracked rotor...but it has not always had this problem...which makes me think that something has gone bad that is causing it. Back when i didn't have things like an ECT (coolant temp sensor) and the swap was in its infantile state, the car revved very beautifully, but didn't necessarily idle or start well...now those positions have switched and it starts easy every time, and idles relatively smoothly, but will not effing rev.

AR is an air fuel gauge.

Pull the injectors and soak the in sea foam for a few hours then rinse with carb cleaner, reinstall with new O rings.
Lifters should be fine, replace the push rods with chrome moly ones.

Have the car tuned with the Big TB. You've got it Use it.

Stay with the bigger intake tubing,

Your motors fine, You could have the same problems with an LS1. And you'll send a lot more money.

cool, this is exactly the answer i was hoping for.

One of the things that i desperately need to check soon is my 02 sensors, because i haven't replaced them or checked them since i had my really bad backfiring problem with the bad opti...so if one of them is toast, or on its way that could be contributing to my problem.

They could, but your computer would have to be driven long enough to go into closed loop mode for them to become affective.

In regards to the injectors....
If they are a larger Bosch type, then send them out to have them ultrasonically cleaned and tested. If they are the original rochester injectors....toss them in the closest field
I have used this company several times for cleaning [You must be registered and logged in to see this link.]
I have used this guy with great results... [You must be registered and logged in to see this link.] ....almost cheaper than paying to clean your own 8 injectors.

Did a little trial and error the other day, and i learned a few things from a local LT1 guru that i stumbled upon at a Porsche meet (fancy that huh?)

I swapped my old PCM back in, which didn't have the emissions related stuff tuned out (Brandon at lt1swap.com missed that stuff) and the hesitation is 95 percent gone.

Here's what happened originally:
I had this computer that I put an LT4 knock module in tuned by Brandon Patten. It was just a baseline tune to get the thing running (got rid of VATS, tuned out a couple of 02's, the usual). Well this PCM always ran a little rich. I believe this was because I didn't have a couple of sensors hooked up which caused some closed loop/open loop issues. I installed those sensors, but also picked up a new engine computer, all while the opti was getting ready to grenade on my ass. When I pulled the motor to freshen it with new seals, timing chain, valve springs etc (after the opti blew up) I had the extra PCM tuned for free by Brandon. I swapped this PCM in and installed the LT4 knock module in it, and since then the car wouldn't pop or crackle on decel, and had this nasty hesitation (sounds like a lean condition huh?).

I decided to drive the car back to the garage last week, on one of those gorgeous fluke days, and swap the PCM, because in addition to the problems listed above I haven't been able to connect to the PCM via OBD2 stuff (wiring or PCM, had to narrow it down).

I swapped the original PCM back in, fired the car up, still wouldn't communicate with the OBD2 scanner on my computer, so it's the wiring..."damn" I thought. I almost turned the key off, but had a moment of clarity, reached over with my hand (I was sitting in the passenger seat) and gave the right pedal a bump...the car revved up pretty nicely. Well I'll be damned! I took it for a drive, and it pulled like hell, didn't backfire, but I got that nice sexy "pop pop crackleackleackle" on decel...yummm, sounds like it's running happy!

There's still a little bit of hesitation/unsmoothness (best way to describe it really) when I snap the throttle from idle, but if I just touch it (5 percent throttle maybe) before I snap it open, no hesitation.

The conclusion. I think I still have some tip in problems, even with the stock throttle body, but that may have to do with having an open crankcase. I learned from this local guru person that the fuel trims on an LT1 motor can get thrown off by a breather being put on the valve cover instead of the PCV valve (or whatever it's called). I also learned that the clocking (rotation) of the MAF can influence the fuel trims because of the differences in density and speed of the air moving through curves in the air intake.

Thoughts?
Ethan