My 94 firebird is hard to start and pops and backfire threw exhaust on hard acce

What is your question?

Car ran fine decided to do tune up plugs wires oil air filter ect.so after that car still ran great then noticed coolant leak behind timing cover so tore down to fix noticed timing can stretched so replaced put back together noticed at wot it acted like starving for fuel couple days later driving Down the road I notice tach starts to jump and then car start to miss real bad then backfire threw exhaust an dies got to start back up but on runs if lite on pedal hard acceleration backfire and pops past 3000 rpms any help with this is greatly appreciated