99 chevy 1500 5.3l rough idle cold backfire, warm runs fine
 

Question,

Ok when i started the truck this morning or any morning, temps about 50 degress. but when warm runs fine. Trucks over fueling

Truck chugs can't get it above 1500 rpms without it backfiring, but when warm it runs fine> It's got a code for system lean bank 2 sensor 2, but here's my question, cats have been hollowed out and rewelded, if i put a new oxy sensor in it will it fix it? or because the cats have been removed will it be a waste of my time? im not sure how these chevy's work> or is it even the oxygen sensor, guy told me when i bought it, it needed a new cam sensor, it was about 100k ohms off of resistance but didnt seem to change anything.

Also could an exhaust manifold leak cause this? someone told me it could Just wondering.
I do have one>

Or what about putting a spacer between the oxygen sensor, to get it out of the exhaust main stream?