well yesterday when we put the asm long tubes on my truck i had the same problem the had the exhaust wellded up and long fuel trims were staying at +17.5 so when i got home i pulled the front two 02sensors unpluged the maf and put the 02 sensors in and drove it this morning long fuel trims are at -2.3 at 75 and 0.00 at wot.

after you get the exhaust welded up clean the 02 sensors and unplug the maf then start it up after that you should be good.. after you replug the maf and put the 02sensors back in lol