Sluggish Truck

1996 GMC Z71


Vortech 5.7 (350)

Custom Dual Exhaust

This truck ran great but the mufflers (cheap turbos) were rusted out. I put new turbo mufflers from Thrush on and now the truck is really sluggish on acceleration from a stop or while moving.

Does this show a different problem that was masked by no mufflers or is it something else?

Contrary to popular belief, open noisy mufflers are not always the best performance option. Having wide open exhaust will reduce the exhaust backpressure which might give a bit more power at higher RPM’s, but will actually reduce the low-end torque, which might be part of what you’re feeling.

However, if it ran okay with everything rusted out and the old exhaust system was comparable, it might be something else. It could be a plugged catalytic convertor, especially if your old cheap exhaust system came with “performance” catalytic convertors.

I don’t have wide open exhaust. Turbos are not straight through mufflers. When the last set of turbos rusted out, it appeared to run fine. When I replaced them with another set of turbos, that is when I encountered the problem with the truck being sluggish. I gotta mash the pedal in order to get the truck to take off. If I don’t, it just chugs until it is up to speed.

Any “Check Engine” lights? Did you remember to reconnect the oxygen sensor?