I used the search option to look up information on the SES code 42. TO start off I have a '87 IROC-Z that originally came with a 305. I replaced the 305 with a 350 from jasper. I tried using the stock 19lbs.injectors from the 305 but it spark knocked (wasn't getting enough fuel). I called Howell EFI in michigan and they sent me a chip that fixed my spark knock problem. However after that chip i decided to install the recomended 22lbs. injectors. I am still running the chip used for the 19lbs. injectors with the 22 lbs. The problem i am having is a misfire and a fluctuation in the rpms that can be seen with the tachometer. It is fluctuating between 1200 and 900 rpms when i first start up the engine. while the engine is running you can here a "popping" or a misfire sound if you stick your ear next to the exhaust. I have replaced so far the distributor, coil, ECM, plug wires, spark plugs and checked a couple wires. What else is there that i can check or replace?

the first thing i would do is go back to the old chip and see if that does anything.....i know it can be a PITA to pull the ECM back out but i would start there since you are using the right injectors now

I went back to the stock 305 chip. It made a noticeable diffrence in power all around the RPM range. I am still hearing the "popping sound" coming from the exhaust. However my exhaust manifolds are warped on both sides of the motor. I ordered a set of hooker 2055 headers but they are on backorder and jegs said i should receive them in a week or two. But even though it has an exhaust leaking it still shouldn't be "popping" correct?

You might want to recheck your timing it will cause the pop also you said the manifolds are warped they can really be the cause

What should my timing be set at? I currently have it a 6 degrees advance.

stock timing is 6* BTDC i believe with the tan/blk bypas wire undone for timing

does anyone else have any more ideas on what i can do? So far i have replace coil, distributor (including ignition module), spark plugs/ wires, and even cut out the disconnect point to check timing and used a connector to form a straight wire just in case the original disconnect point wasn't causing me any problems.HELP!

The car misfires while driving down the road. Originally i thought it only misfired when at idle. But just recently i stomped on the accelerator and my tachometer went crazy and the car surged a little bit and seemed like it misfired a lot. This has happened before but it seemed like it went away. Any ideas? i really need help on this issue please!