Sierra loss of power

[Deerassassin]

I have an 03 Sierra 1500 5.3 and installed a cutout which uncaps the exhaust. It feels that I lost power even with it closed will a programmer fix this. What should I do?

 

[Molson02536]

I have an 03 Sierra 1500 5.3 and installed a cutout which uncaps the exhaust. It feels that I lost power even with it closed will a programmer fix this. What should I do?

Bring your Sierra to a speed shop that can Dyno tune your PCM. A hand held tuner will only do so much tune and a wast of money for extreme tuning cause they still need to follow guild lines to what tunes can be done to follow EPA regulations.

The Vortec engines take readings from the sensors throughout the engine and runs on vacuum, that's why you can not really go radical with a cam swap without major PCM tuning. With the cutout you dropping your back pressure passing the parameter of your stock tune and your engine's fuel system and advance timing which can not compensate for the lack of back pressure causing your engine to lose power.

Take note that modern engine's PCM's are tuned with the stock exhaust flow rate, that is why when you blow a muffler or replace it with a higher flow system which you lose to much back pressure. You end up with less HP and Torque until you get up in the high RPM like above 4,500 where your PCM no longer uses reading from your O2 sensors and MAF sensor, but who wants to be driving in 1st gear all the time through out town waiting for the valve valve train to fail and your doing a valve job within a year.

Good luck and keep us posted.