Have you checked the voltage touching the battery posts and then only touching the cable terminals? If they are badly corroded, there will be a difference in voltage.
Yes, like DaveP said. I do have a shift kit also. I have a mod govnor also, shifts at 6k. I have a 3" down pipe into a 3" cat (fake) into a 3" muff, into 2 2.5" tail pipes, all stainless. I have zero backpressure at 16 lbs boost.
I have a xtang cover on my Sy, and I wouldn't trade it for 10 OEM covers. The best thing, IMO, is that the xtang snaps all the way around, also the rail snaps are adjustable for a tighter or looser fit, and there are 3 bows, instead of 2.