Ok so here we go!! I have a backfire/misfire issue and its becoming a headache. It only happens under a load to. I got it back from the dyno last month and it was running perfect. The only changes I have made is a 4/6drop kit. I did have to weld on frame and I'm not 100% sure that I removed the negative side of the battery. I've read online and looks like it is pretty rare to damage a ECM from welding on the frame with out removing the battery but im sure it can still happen. I don't have all the grounds like a factory car so I guess that could be a possibility.

I also found 1 of the wires that goes to the crank sensor got burned on the dp. I was almost certain that was the problem so I fixed the burned section but I still have the backfire/mssfire issue. Could the burned wire being grounded or shorted out on the down pipe ruin the crank sensor or cause problems in the ECM? Any thoughts or advice will be greatly appreciated!!

Also it is not throwing any codes. STUMPED!!!

I've checked the plug wires with a mulitmeter and on the 20k ohm setting the longest plug wire came in at 1.03 and the shortest one came in at .37 . No of them looked out of the ordinary

It has new TR6 plugs

Fixed the burned crank sensor wires

Also checked the compression of each cylinder and they are all within 15 psi of each other. They are pretty low but I want to say its because of the compression. I'm going to go back and look at the build sheet but I want to say it was lower the 8.5:1 CR. Most of them were in the 85-90 psi range and a few of them were at 102-105 psi. Maybe weak springs?

Ok just checked and my motor is at 8.3:1 pretty low but I guess that would be the reason behind the low numbers on the compression test?