ok so i did some searching and found nothing my buddys 91 z with 305 5 speed TPI is running like hell. it runs like it is a 454 with a lumpy cam in other words its runing like its missing and stuttering alot. he says that it is ok after around 3 grand RPM. we changed the cap rotor and plug wires and plugs no luck. i have searched and came up with it could be the coil or the IAC sensor which i have no idea where it is. please help.

thanks ahead of time

 

so we took it for a spin and came up with its missing due to he has a header leak on one cylinder and you can hear that its missing. also thre is a bad gas smell and a little backfiring he has an electronic coil checked the connections and their all good.

 

Check for intake leaks. Put a vacuum guage on it to find out for sure.