First idle problem now bucking
 

Hello all, I recently purchased a 94 fd that is in very stock unmolested condition. Just has a down pipe, and car back straight pipe. At first the car was only making 4 psi of boost and I tracked down a torn coupling on the charge piping, fixed that and it ran excellent for about 2 weeks. Then out of the blue it started having a very low idle while hot, it was like a lope almost the battery light and dash lights would start coming on when the idle got real low. So I replaced the spark plugs, and checked TPS readings and they were all within range. After reinstalling the spark plugs now the idle while cold it loping still just at a higher Rpm, prob about 900-1100rpm. It's blowing black smoke at an idle, tried taking it for a ride and now it bucks and really doesn't want to go past 3k rpm. I am still In the process of learning the main go to items to check on these cars, but if anything rings a bell with anyone that would care to share any input would be greatly appreciated. Thanks!

Yes, instantly a free flowing exhaust on a stock ECU come to mind. Instant trouble.

Even after running great for two weeks? The car came with the exhaust, I didn't just add it