I bought a 1997 Z-28 thats pretty much stock. it has always had a evac code and i had problems starting. after replaceing the fuel filter, pump, regulator, and injectors the problem is fixed. but i still have the evac code coming up even after having it cleared. the new injectors are 24lbs venom. when i replaced the old one with the new ones it started showing a misfire on #7. i took the injector out and replaced it with a stock injector and it straightend out. so i took the injector to be repaired and the said it was alittle off but not bad. so i put the injector back in and the same problem. i swap the injectors around so the "bad injector" was in the #1 possion. same problem, misfire on #7. so i know its not the injector but why does it run fine with the stock injector but miss fires on #7 only with all after market injectors? and why the evac code? any help would be great. im lost at this point. oh and i have replaced the wires and plugs.

 

It sounds like a mechanical fault with the injector. As for the EVAP code, get it scanned. There are several DTCs that apply to that system.