Need some help!!!

1991SC

Registered User
I have just completed an engine swap in my sisters 91 SC. The only engine I could find was an 89, it took some swapping of parts from the 91 engine to the 89 to get it in and running. engine harness, crank trigger, egr blank off plate. but it went in and runs, the problem I am having is when you step on the gas and the boost climbs to 5 lbs. the car breaks up really bad. I have tried changing coil pack, air flow meter, plugs, checked for vacume leaks, I can't find the problem. I am at my wits end here and need some help form some super coupe people, this is the first one of these I have done usually stay with Mustangs but she needed an engine so I put it in for her. Please give me some ideas on where to go to next!!! Thanks,
 
im thinking clogged cats , or down on fuel pressure pump or filter or regulator , or plug wires , maybe just old gas if it took a while to fix maybe try stp gas treatment
 
Thanks to all who replied, I changed the plug wires today and the car runs great. still don't quite understand how that works, it idled fine with no miss but when it was boosted it was terrible. At least the wires fixed it. Thanks again. John
 
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