does it matter whether the rear O2s for OBDll cars are in front or behind the cats?? or alls they have to be is hooked up??.....also will i need a computer reprogram for Longtubed headers?

 

From the factory the rear O2 sensors go behind the cats, they monitor whether or not the cats are doing what they're suppose to. So they wouldn't do much good in front of the cats.

If you're getting long tube headers, you more than likely won't use the rear O2 sensors (especially if you're running w/out cats), in that case just get a set of O2 simulators. They just plug into the old rear O2 sensor harnesses. Or you can program out the rear O2 sensors, then you would just leave the rear O2 sensors unplugged.

 

O2 sims are about $100. A tune from madz28 is $125 plus 20 HP. I would to the tune to eliminate them. Plus he can tune out the EGR and AIR that you are probably going to remove anyway.

 

Actually im keeping EGR and AIR fro emmissions purpose.......i am fabing a catted y-pipe and if i get the O2 sims i can still pass emissions??? withthe o2 sims that is ? i can use sims with catts also for the rear?

i can get around visual inspections but emmissions is a hard onein my area...but i want LTs really bad so im willing to take a risk while keepng all emmisions hookups

 

You should still be able to pass with O2 sims, they won't effect how your car will run.

 

thank you......quick question

im thinking of getting pacesetter long tubes and i want a catted y-pipe.....would it be cheaper to fab a y-pipe or just buy an ORY and two high flow converters and cut and weld?

 

That depends on how much a local shop would charge. I'd get some estimates first, then decide which is cheaper. Chances are buying the cats online will be the cheaper than at the shop though.

 

thanks man ,........

do i really need a LT4 knock module when i get LT headers
?

if i do where can i get one?

 

You won't know until you get the headers and install them and THEN scan the car to see if you have knock retard. After that, a simple test with race fuel 'should' be performed to see if the knock retard is real or false. THEN, after all that and determining that the knock retard is false is when you'll know that you might benefit from an LT4 knock module