So I am new to this forum and to the Altima. So here it is I recently bought a 07 3.5 Se with a six speed and the previous owner had the firewall cat replaced and then he started having trouble where the car would just bog down and stall out when u give it gas. He was under the impression that the right front cat was no good. But when I got the car home I did not have a p420 code I did have a p1156 code that was the upstream O2 sensor and a p335 code so I replaced both O2 sensors and the crank position sensor and a new battery. I now have no codes but still can't drive the car. Any ideas ?