When I step on the gas to try to pass, it sounds like my entire engine gets a low roar and muffles itself and I don't receive any real power to push the blazer uphill too. If I just increase the pressure to the gas pedal I'll get moving but if I step on it, nothing but that weird sound. I havea new cat converter and gibson exhaust I need to install, just wanted to know if the exhaust is choking the engine. Could it be the air filter?

 

There are a lot of possibilities here.

When was the last time that a full tune up was done?

Have you attempted to clean your MAF sensor? If not, then I would recommend that you do so. A dirty MAF sensor can cause all kinds of drivability concerns. Let me see if I can dig up my explaination of how to properly clean the MAF sensor for ya...

Ah here it is: Tune up, what all do you do? - post #2

Let us know how it goes!