i recenly rebuilt the engine in my 89 camaro iroc z and have lots of experiance with that aspect but am not with the sensors and all that i have the tpi but something is not right when i let off gas it has a shake i was told by someone that it might be the mass air flow sensor or another sensor but i dont know where to start

 

if thos symtoms dont help much i have some more deatailed ones it has a missthe bottom end rpm is vey jerky and surgy and i know its a v8 but its very very bad on gas like a trip across town not taking it ez but not abusing can take about 1/4 of a tank of fuel

 

Did you make sure you set the timing in the correct manner? assuming it has the stock engine it would have been a tpi motor. To set the timing correctly, you need to disconnect the EST connector on the passanger side of the engine in the wiring harness. It will be the connector on top of the heater box, with only one wire in and out, Start the car, and then set the timing to 0* TDC. (That's what my tpi calls for on the underhood sticker. If you are sure thats not your problem, check that you got the firing order right. (Spark plug wires on the correct spark plugs.)