Hey everyone im new to the site. I'm on my second maxima and i had a question that my mechanic cannot answer for me so i thought i would see what anyone on here thinks. I have a 2000 maxima se. I have a full cat back exhaust on the car and cold air intake and had the mass air flow replaced and the car ran good ripped up first gear just by rolling on the throttle, not bad for 105k miles. now i went and spent money on a y pipe and high flow cat. paid to have them installed on my baby two weeks ago. left the garage and the car is a PIGGGGGG. i mean your supposed to gain 10-30hp with both the y pipe and cat replaced. i seriously think i lost 30 hp. a few days later the CEL came on and i havent had time to scan it but since then it has ran a little bit better but it is still a pig when you compare it to just having the intake and exhaust on the car. all plugs were replaced 15k with OEM and all ignition coils were replaced as well cause it had that notorius ping from the crappy coils being bad. anyhow if someone has some advice please fill me in. emails would be great thanks

 

Check o2 sensor.

 

same here, was the battery unplugged during your install? did u find out what code it was? reprogramming ur ecu for a bunch of money should get rid of it if it is an o2 issue if the o2 is really good and the ecu is trying to compensate for it.

 

no y pipe and free flow cat will give up to 30hp. if you had that expectation then i understand the dissapointment. i know you said 10-30 but it is more like 10-15 depending on car condition, tranmission type, etc. get the code pulled and go from there. with a y pipe install, they should not have been messing with any primary o2 sensors but it is possible that it just failed. of course, there are a ton of other things it could be. just get it pulled and report back.

 

Get it Pulled, Or Reset Ecu, and see if it comes back....