is it lag in throttle response that leads to poor acceleration?
like when you press on the gas the car would just make a sound but not go?

i think this is happening to me after i got my exhaust

 

An exhaust should not be causing excessive knock. It's just a simple bolt on. Plus our cars have built in knock sensors that pull timing if it detects knock.

Knock will make a slightly audible tapping sound. Your car will lose power, and you will damage the motor. The remedy is higher octane gas, colder intake temps, and retarded ignition timing.

Try resetting your ECU (disconnect the ground for about 2 min with the door open). Then when you start the car let it idle for about 15 min before driving it. It'll help your ECU relearn the fuel curves with an exhaust on it.