Hello everyone! I’ve been lurking around this site for a few weeks and figured I’d introduce myself. My name is Dave, but my buddies call me DOC (“Dave-On-Call”). Five years ago I retired from St. Louis to Georgetown, Texas. I need some TBI advice and or education as I’m at a point where I’m in over my head. My project is a 1948 Chevy 1/2 PU resto-mod. I’ve owned this truck long time and did pretty much everything on it myself. I’m a gearhead. Here’s what its got: 1969 2 bolt 327 (.030 over; 10:1 forged pistons); small valve Power Pak heads and a stock cam, cast iron exhaust manifolds; Magnaflow exhaust; 700-R4 from a 1991 Z28; 3.73 Posi. I’ve been driving it about 7 years and put about 5000 miles on it. I’ve gone thru a Dualjet, then Q-jet, then a Holley carb. Quite a while back my daughter’s ex-boyfriend abandoned his clapped out 1992 GMC S-15 in my garage and so I inherited a complete running TBI 4.3 Z motor. (ECM 16144288/Prom BARL). So, looking for a challenge I decided that the 4.3 fuel injection could work on my 327. (Why can’t you use a V6 Computer/Prom on a V-8 truck?!) It took some time, but I pretty much took everything ECM related from that S15 and put it on my truck, with the exception of the distributor, of course. It’s a stock GM EST distributor, with Electronic Spark Control, from a 1990ish C10 5.7 K motor, using a TBI intake from that same generation truck.The EGR is fully functional. I’ve installed a CE lite in the dash and have a fully functional ALDL under the dash. I can monitor all of the ECM inputs and outputs using an OTC Monitor 2000. I’ve logged about 4000 miles with the TBI. But here’s the trouble: as I dialed in this computer system I gradually started experiencing a very random backfire/stalling problem from a stop, just off idle. When driving it with a scanner I’ve discovered that the scanner RPM is about 25% greater than my SunPro tach reading, which kinda makes sense, considering that the V6 ECM is interpreting a V8 RPM with 25% more cylinders. Real early on, at the throttle body, I accessed the throttle plate stop screw and manually set the idle to about 550 rpm in gear (per my tach). However, IAC/RPM on the scanner shows the engine is turning faster at around 700-800 rpm, and accordingly the ECM drives the IAC to Zero. I hit the gas from a stop and then sometimes, randomly, it will backfire and die/stall, like maybe the sudden throttle opening doesn’t support enough fuel and it goes lean; or is it getting too much fuel (rich?) and stalls. I’ve got a 1991 GMC Light Duty Truck Emissions Manual and comparing ECM Pinouts between a 4.3 Z motor and a 5.7 K motor shows that almost every terminal and circuit is identical. (EGR is different as a 4.3 uses a ported EGR valve while a 5.7 uses a negative back pressure valve). Researching this site determined that a 1227747 ECM would maybe be a good candidate for a swap as it is used on both the 4.3 and 5.7. I found one on Craigslist with an ANLW Prom. Anxiously I installed it: only to barely made it around the block (&^%$#!!). Bad ECM? (Note: I did have the vacuum supply to the EGR plugged). As of late, with the 4.3 16144288 ECM back in place, I’ve raised my minimum air rate to about 600+ RPM in gear, have driven it about 100 miles and it runs GREAT: at highway speeds. No CE light, goes Closed loop, and cycles Rich/Lean. But at around 25-35 MPH it has a bad surge. Accelerating with normal throttle from a stop I get a sag and surge also. Another issue I might add, is that my fuel economy is maybe 13 MPG combined. Which brings up another question: with the V6 ECM saying the engine is turning 25% faster than it really is, is the ECM not only closing the IAC, but is it also commanding too much fuel? Should I try another 1227747 ECM/PROM? Or is there a better ECM/Prom combination in view of the drivetrain that I’m running as described above? Or can someone burn me an appropriate prom? A prom that will work with the 4.3 V6 ECM to correct the “false” RPM reading? Or does anyone have for sale a known good ECM/Prom combo that will work with my drivetrain? Guys, sorry for the long post. I’m hoping that someone can point me in the right direction. Also, FWIW, I’m not technical enough to even begin thinking about getting into burning my own prom; I’d rather not go there. I’m at an age/stage where I just want to enjoy my old truck. And I’d really like to keep it GM TBI fuel injected. Thanks in advance. Regards, DOC