We just bought a stick shift '88 Iroc. The engine has been swtiched to the large block (350 ci 5.7 ltr). It hesitates and will not pass smog. We have put in a new computer and changed the mass air flow sensor. A mechanic told us that in that year, only the automatics came with the big block option.
He says there is a 'burned' chip that can be put in to help the compter 'see' and 'read' the big block so it will smooth out and pass smog. It is currently getting too much gas to pass. Does anyone know if this is true and if so, where can I buy one? We are anxious to get the car running and start restoring the body... please help!

http://www.thirdgen.org

283 , 302 , 305 , 327 , 350 , 400 are all chevy small blocks by the way. Common big blocks are 396 ,402, 427 , 454 , 502

if your 350 is fully installed with all fuel injection and smog equiptment u shouldnt have much trouble

Your mechanic is correct. only 305 engines were avaialble with a manual trans, all 350's were automatics. A custom chip will dail in your tpi system right, and thirdgen.org would be the place to find out where to get that chip from, unless your mechanic had experience with such things.
It seems strange for it to be getting "too much" fuel, tho.
With a stock 305 tpi and computer on a 350, I'd expect it to get too little fuel, which could cause high HC due to a lean misfire.
It's also possible that whoever did the engine swap modified the efi system. Could be as simple as raising the fuel pressure with an adjustable regulator. It might be a good idea to start checking and verifying parts numbers and see exactly what's in there.