I had a rusted out pipe just in front of the CatConv replaced. This re-routed the exhaust, likely for the first time in years, into the muffler. (I just bought it, and was wondering if all 89 F150s are that LOUD.) Now I can hear myself think in the cab.

Here is my puzzlement. It might just be my imagination, but I swear that both the rough idle and the surging acceleration are both now noticable smoother.

?????

 

Possibly. Without a pipe and muffler attached you might not have had the proper amount of backpressure the engine likes. This can cause lugging and loss of power.

Also, it's probably quieter and vibrates less. That lack of noise and vibration could be part of what you're noticing.

 

Yea having a fully intact exhaust system makes a motor run better then one that lacks a muffler and or a tail pipe or one that just leaks really bad.

 

My guess is that the exhaust is now scavangig itelf due to the tail pipe where as before i was not. That scavenging can make a big difference in performance.