96 cobra running rich problem/backfiring

[mikeyzx6r]

ok guys so i have a 96 cobra with a kenne bell set at 8psi i put the car on a gas analyzer to read how much hydro carbons (unburned fuel) were coming out of the tail pipe bank 1 read about 1200 ppm at idle but bank 2 read 3200 at idle so i pulled the plugs to read them after bank 1's plugs looked perfect but bank 2's plugs were running super rich what could be the problem of each side of the engine having different plug readings and could this also creating the problem why the car backfires sometimes in between shifts?
any answers will be greatly appreciated

 

[wmburns]

Has this motor been recently re-timed?

 

[1987stangman]

What do the fuel trims look like on that bank on a scan tool?

 

[mikeyzx6r]

the motor has different cams in it so i would imagine that it has and i have yet to have it on a scan tool