So i replace the throttle sensor on my 05 infiniti do the relearn then started idle bad like is missing o fire on the plugs check engine light still on obd read po300 miss fire n change sparkplug but still doing the same now the cathalistc cnvert is get red hot can some one tell me what wromg now

 

Cat turned red means a LOT of unburned fuel is being shot into it, strong possibility that you damaged the cat. Multiple misfire, are you SURE you hooked up the correct wires to the correct coil packs?

I definitely wouldn't try to start the motor again until you find out what isnt hooked up right!