I did a desmog, as well as a Cat delete, and 3" exhaust with a small muffler. Did I notice any performance!? Yes! Not night and day, but the throttle response has greatly improved. Over the last 10 years of owning the truck it as gotten 9-10mpg. I recently did a 200 mile drive, towing a bike up to a buddies house. The truck got 11.4mpg. That's a 12% increase in fuel economy while towing. Not bad. I'm happy with the mods I have made. Hope you have similar results, let me know.
I just finished up with mine last night, got a little side barred away from my project for a few days, $h!t happens.
Good news is the metal air line that once was connected to my header is in the bed of the truck! Definitely a noticeable difference...could be the new headers helping out in that difference too lol. Only one hucup which I’m about to go check out once I submit this is my truck is idling more than rather high (1500rpm) it idled high before (1100-1200rpm) I figured that was caused from the old exhaust manifold that was leaking and figured it would drop after this....well I was wrong! I’m thinking of there may be a vacuum leak somewhere, that’s where I’m going to start anyway.
And as far as more performance adds, this is where I’m at thus far. Obviously did away with air smog pump and installed new headers, 3” exhaust with cat removed (no inspections in Florida!) to a dynomax muffler, K&N filter & air horns cut out, upped fuel pressure via adjustable pressure regulator made by aeromotive, 180* thermostat and I bumped my timing up to about 13-14 from 10 BTDC. Once I get my rpm’s to drop I’m going to rock it like this for a bit, allow my bank to build back up and then I’ll be looking into getting some good headwork done along with an efi cam and new intake. Parkland performance Auto Machine is where I’ll be going for those mentioned mods.