i have a 87 N/A automatic. i want to do a full cat back exhaust and i local shop said they needed to look at if i have more than one O2 sensor. he said some models have more than one . so where exactly is the O2 sensor? is it before or after that second cat. we are trying to elliminate two of the three cats. putting in a high flow cat. also what size do you recomend? 2.25 ? i have read some threads saying 2.5 is to big . please let me know.
thanks again.

also what can i do to make the car shift harder when under full throttle? or to make the tranny more beefier?
thanks again
andy

 

Oxygen sensor is in the exhaust manifold. Open up the hood, go around to the passenger side and look down near the firewall. That thing with one wire coming out of it is the oxygen sensor.

 

Oh yeah... if you want a beefier transmission, do a 5-speed swap. Those slush boxes do not tend to last very long.

 

so i can tell the muffler shop here that there are no sensores he has to worry about in the exhaust system right? he can basically replace all the exhaust pipes and then just put one high flow cat on right? thanks for the help again.

also what size is the stock exhaust pipes and what size should i get ?

 

Yeah, you do not have to worry about the oxygen sensor unless you are putting a header on your car. You can replace all the pipes and put a hi-flow cat in, but there is something you should know. If you want your 5th and 6th ports to acutuate you have to that split air pipe plumbed into the cat like it is now. That pipe provides the backpressure that is need to open the 5th and 6th ports when you increase the RPMs above 4,000. If you are not worried about losing 15 HP or you can monkey-rig it so that you can actuate the ports a different way, have at it.