Did the throttle body bypass on my 1994 z28 and descreened the MAF to test gains and loses. After doing so drove the car for around twenty minutes then it developed a stumble at half throttle so pulled over and put the screen for the maf back in (100% sure maf was not damaged) tried to crank car but would not completely turn over after a few tries it cranked but shut off sounding like something was preventing air flow. Tried starting again and back fire and smoke poped out the throttle body a few times then car evened out and started roughly (leveling out after a min.) but on trip home it had a lack of power and was stumbling on accel. next morning car cranked fine but still a noticable lack of power then driving home notice smoke coming from tail pipes and oil filler. I have a small exhaust manifold leak(changing gasket now and replacing spark plugs) any one with input on wat could be going on please advise ASAP HELP NEEDED!!!

 

you sure you did the bypass right....and did you put a rag down under your tb so no coolant would drip on your opti.....sounds to me like this happened and its ruiend your opti.....but it also happened to me and it dripped all over mine...i just happened to figure it out quick and nothing else like that has happened. thats just my suggestion...GL with it though.

 

Vacuum leak? Make sure you didn't leave anything loose...

 

It can be pretty easy not to see the elbow over the throttle body correctly. Check over all of your connections. Also, descreening the MAF is generally regarded as not being a good idea.