I have this 2000 firebird v6 thats no good acceleration and vibrating.?

i got water in the gas a while back and it ran like crap i had to replace the plugs and wires and fuel filter and a couple coils. now it runs and has the power to go which it did'nt back then but now im hearing this sound beside or inside my cataylic converter its shaking and my exhaust tips are shaking also. i first start my car up the motor shakes and vibrates and makes a ticking sound but it goes way i think thats the oil to lifters. but it seems like it still dont have that good acceleration like it used to and wats cause the vibration on the exhaust and motor and help is appreciated. Thanx for listening