Well my mac short tube equal length header were cracked. They ran into the stock y pipes and cat running into 3 inch and my flow mastser. So i picked up a set of hedmans headers and built a y pipe from 2.5 in to one 3 inch thru a flow master no cats or AIR pipe. I had major fit problems with the headers and needed to modify them and i installed the O2 into the left bank collector. i also replaced the plugs due to me cracking one. So i fire it up and it seemed like it was running rich and igniting the fuel in the pipes. I would add that this is a 93 ford F150 5.0 (Stroked to a 347, w/24lbs injectors, hand ported E7TE heads,) running a diablo delta chip that was dyno tuned in wisconsin it ran ok but never seemed perfect the gas mileage was never that good. i have since moved to wyoming and the elevation to 4000+ made matters worse and i was only getting 12mpg, but was never popping before i pulled the cats and stock Y pipe set up. It seems rich but is not throwing any codes i'm really at a loss and dont have any way out here to do another dyno tune and reflash the chip.

 

What cam does it have? If it's nothing too radical I suggest you pull the chip and put 19lb injectors back in it.

 

When i built the 347 i put the 24lb injectors and it was lean on start up and generally ran poor. It has the Ford Explorer 5.0 camshaft. I had a old desk top dyno and it worked pretty well compaired to most of the after market cams. Not saying it was the best, but it made very good low end power. i actually put the 5.0 explorer cam in when it was still a 5.0 and it ran lean and knocked so bad it busted the #8 plug thats when i installed the diablo chip and had it dyno tuned. I had it redone when the cubes were bumped up. i was thinking of tryin a 5.8 lightning computer C3P-2 and running 19lb injectors , plus the L computers have better support over the Bast#rd Z2D1 computer thats in it now. That E4OD really puts a crimp into my computer options with out buying a stand alone controler.