I have a 95 z28 six speed. Ive narrowed down to when i first drive it if the engine is completely cooled off it will bog down a litte bit, but once it warms up it pretty much goes away. But, if I get it warmed up, then turn it off for about 30 minutes ish, it will spit sputter BAD. I mean like it barely wants to move and it jerks around. But once again when it warms up it gets mostly better.I have replaced the plugs, wires, distributor, water pump and scanned it. Every once in a while it will throw a ses, but go away. It said it has an EGR issue. I have already tried a new solenoid, but it didnt change anything? Does it sound like a valve could do all this? Also, if im going about 60 and I downshift to 3rd, it will bog down, btu if I go to 4th it goes better. Sometimes it feels like full throttle bogs down too. HELP

 

check your fuel pressure when its acting up on you. it may be that once the pump is warmed up its getting weak and not pressuring up like it should. might try an pull an 02 sensor and see if its fouled.

 

aldlcable.com and get a cable and datalog it. You'll get a wealth of information

 

I replaced the EGR valve and it didnt have the problem it had when its completely cooled off. But then i drove it 30 minutes later and it sputtered. Not quite as bad as before, but it went away quickly as it warmed up.