My Camaro has been shifting erratically from 3rd to over drive while driven at about 40-50 mph. A couple of weeks ago, it stalled while shifting from 1st to 2nd and would not start back up, it posted a code 13. I disconnected the battery to reset the computer and had check the wires from the TPS senor and the O2 senor both were ok. It had a strong exhaust oder when it had warmed up so I installed a new O2. It idals erratically I check the fuel injectors and they tested good. Also the timing and spark plug wires are good also. Am I over looking something ? Please Help me. Thank You.