I have a 92 dakota 3.9 that's originally and auto tranny, now manual. No retune done and for the last year everything has been running great. Recently is seems to jump into limp mode. Maxing ram at 4100 and you can definitely tell something is getting restricted. If I'm going anywhere between 50-70mph and downshift into 3rd to tranny brake, it will pop and backfire(piped out of the side after cat) then I'm right back to full power and stock redline. Also when you're driving you can tell by exhaust when it's having issues. At 4000rpm when it's struggling and petal to the metal it sounds like a jet in the sky. When it's running properly obviously sounds like it should. Any assistance is much appreciated.

 

Still have the cat on there?