Ok, i just gutted my cat and my car threw a code 51. The car hesitates like crazy now. The code page says im running lean. Its either the map sensor(i thought it threw a code), injectors, heated o2(again thought it threw a code) and a few other things. Now before i gutted the cat i had a cel for an o2 sensor but the car did not hesitate at all. Could this just be the map sensor going bad? The car has 137000 miles and its never been replaced. Yes i know i should replace it but i just want to make sure its the problem before i dump money into the car again. On another note, when its cooler outside the car runs much better, but still hesistates. When its warm outside the car does it from a start. Any help??