i have a 1992 12valve cummins. i just put a 5in stack on it yester day. and i notice today that when i was going down the road i was in 5th and i droped it into 4th i didnt feel a change in rpm it seem like it and it also seems like i dont have the power i had befor?? say i have a 3in going to 4in up through my bed and then going from 4in to 5in where the stack is. i was wondering it the stack would lower my boost and power??

 

What kind of exhaust did you have before the stack?

 

i had 3in stright exhaust befor. and now i dont seem to get the boost i use to. i was getting around 23psi of boost now its will only get 20. but its seems to take more to get that much. and like i side befor if i was going down the road and was going to pass a car i would drop to 4th but i didnt see a change in power. you know what im saying?

 

Sounds like you just lost a helluva lot of back pressure... Maybe the culprit?