I have a Chevy S10('96) and when the vehicle is warmed up, it is very loud and doesn't accelerate fast from a stop. It's incredible how loud the engine gets and tries, but it doesn't calm down until around 30mph. Then it settles down and drives smooth. Any hints and or suggestions will be grateful. I've started using Marvel Mystery Oil in my oil and gas tank, from a mechanic friend who suggested it. But not till after the noise and accelerate issue.
Although it is impossible for anyone to know what exactly is causing the noise and poor acceleration, it sounds like it may be a restricted exhaust system. To confirm or deny this as a possibility, an exhaust back pressure test can be performed.