Speaking of inspection...
 

speaking of inspection, i have a 94 z28 with a k&n filter kit, magnaflow stainless steel cats, and some other little mods but i cant pass emissions. my o2 sensors are brand new. im trying to replace the old cat with a new highflow one, maybe that will work. my numbers were off the chart last time i went threw. by the way.. the first time i failed for visible smoke i had a broken lifter.. but that was fixed. and it also runs very rich

Running rich is prolly your biggest reason for not passing. Have you spent any time trying to figure out why it's rich? Not only is that bad for emissions, but it hurts your performance and mileage as well.

- Justin

Dont put a high-flow cat on it if you want to pass inspection. An old stock cat will get you through the sniffer easier than a brand new aftermarket high-flow unit. Believe me. I know. I have been running around with a REJECTED sticker on my car for over a year now!! haha

My old 93 was able to pass emission's with a Powerdyne supercharger, SVO injectors, Borla y-pipe, Random high flow cat, Flowmaster cat-back, Jacobs ignition, 160 t-stat and SLP off the shelf chip(not programmed for the supercharger). So you must still have something pretty wrong to be running rich and not pass. Put a scanner on it to look at the sensor's to see if you can find something that indicates why it's running rich.

Fix the richness. That will damage the cat in the long run as well.

???
 

what can make it run rich like that, i already checked the injectors they are fine, and the fuel pressure regulator was checked as well, its brand new. what im thinking is it could be a clogged cat due to the lifter being left unfixed for awhile. and yes im getting about 80 miles to a full tank :-(

I would check the functioning of your O2 sensors. Even new, they might be fouled out. How is your ignition system?

I take it you checked the fuel pressure? What are the 'other little mods'? No stored SES codes? Air inlet temp sensor?

Look for things like a rip in the intake boot after the MAF, bad plug wires, bad O2 sensor, bad EGR. Have you had the car scanned to see if there are any stored codes? Autozone will scan for free.

inspection
 

idk maybe i will just bring it to a mechanic and have them diagnose it for 60 bucks if this cat doesnt work.

Put new cat in
 

well i just put the new cat in and wow its alot louder now lol. also i notice slight better throttle response. it still smells like gas but now it smells like clean gas. well off to the shop to get it diagnosed

well i got it fixed
 

well i got my car fixed the guy i bought the car off of put the spark plug wires on the exhaust and melted them...so i was running on 7 cyls. all my levels are really low cept the nox lvls which are controlled by the egr valve and the cat. i have a brand new egr valve. i just installed a high flow cat so i guess thats why . any ideas on what else i can do?

any at all?