High flow cats today have virtually no ill effects on your flow. At least that's my experience with my wrx and my toyota, and what tuners have told me (And the wrx is protuned) And for those of us in northern CO emissions IS coming back so get a cat on there...

Backpressure is never good but flow is. Smaller pipe allows higher exhaust velocity at low rpms and hence is helpful for low end torque, but becomes restrictive at high rpms and hence limits power up there. Big pipe won't allow high exhaust velocity at low rpms and thereby hurts power down low. This doesn't have anything to do with "backpressure"

Anything that limits your flow like a clogged cat will never be good.

 

Mud hippy:

unbolt everything from the crosspipe, time it in the 1/4 then bolt it back up and run it in the 1/4 and i will promise you it will be faster with the cat vs the open manifold, that is if you dont bend a valve on the first pass.

I agree with the camo about there being a happy medium between too much and too little backpressure and also with the andycrow regarding the exhaust velocity, he was spot on. If you have no exhaust velocity on the 3.0 you will never get it moving

I guess everybody got caught up in the semantics of the word backpressure.

I was mearly offering my experience regarding my gutted cat, everything the same except gutted cat and junkyard cat, mine performed way better with the cat being reinstalled.

 

what channel does the race come on ?

 

I had that problem on my 94 (2 O2 sensors, 1 before, and 1 after the cat), my solution... I had an extra ecu for a 93 with just 1 O2 sensor before the cat, I tossed that in, and now she runs great. The 93 was an auto too....lol


Or, you could try one of these....

http://www.o2simulator.com/index.php...&products_id=9

 

I live in NC, and my truck passed several times with a gutted cat, so its possable. What i think is funny is they do the testing at idle no load, yet i spend most of my time driving my truck, not idling. LOL

 

i know this is a month old but i was wondering what size exhaust pipe you was running at the time. ive heard that if its alot bigger than factory with no performance mods then back pressure plays a pretty important roll.. but this is just from what i heard.

 

i hollowed out my cat recently on my 87 22r and it sounds awesome and even runs a little better. i can hear the sound of my exhaust every time i pass a car and its an awesome sound id have to say haha (drivers exit)

 

TN I hate to say it, but that don't sound good.