I have never redline my car since I got it..i got my engine rebuilt and when in 2nd or 3rd gear it wont rev out cleanly it wont go past the redline and beep..sometimes when im on 1st or 2nd it hesitates to rev like the engine struggles i gotta slow down and do it again and it will go away..could it be the cat converter? sometimes smoke starts coming out of the exhaust when revving it at a higher rpm in 2nd or 3rd but not all the time

 

Yeah sounds like your cat is clogged. Is the CEL on? Year/miles? Last time coils/wires/plugs were replaced?

 

idk where does it say? but the check engine light is on because i need to replace the front o2 sensor and when i was trying to rev it the light was flashing..the car is an 06..engine rebuilt at 152k..the plugs and wires are 6-8 months old..

 

You should probably start redlining your car more often contrary to popular belief its crucial to engine longevity FYI, really don't understand why people don't do this

 

Where does it say what? A flashing CEL means misfire. Misfires ruin catalytic converters FYI

It won't rev cleanly because of the misfires, which could be caused by bad ignition coils, bad wires, bad plugs, a clogged cat, etc.

 

Lucky, how many times do I have to tell you to get that front O2 replaced.

You are damaging more hardware until you do. If it's on order then stop driving till it gets in. Cascading failure is what you keep running into here.