rpm up down why||How to Fix Engine Missing Problem\Blocked Exhaust system 

This is nissan petrol car and the problems is engine missing problem, poor pick up, rough idle etc
so dosto is garhi mai masla ya hai garhi mai pick nahi hai garhi ghut ghut kay chalti hai and rpm is ka up.down huta hai and garhi mai missing buhut zayda hai. plug black hu rahy hai.
so cutmer nay garhi kay plug.injecter.fuel pump.ignition coil sab kuch change kerwaya phr bhi garhi mai koi faraq nahi aya.masla is kay exhaust mai tha.