MAF vs MAP~ Lean Fuel Mixture when swapping 1987 Exhaust Manifold for a 1993 'Shorty' Header

[4RingCircus]

I made the switch from the cast manifold to the shorty header. I think my truck gained some pep, and I like the fact that the headers save some weight. But I have two issues:

1. 4 extra holes: In 1987, Ford put extra holes on the engine head, directly under the exhaust holes. The cast manifold had an integrated 'rail' or 'tube' on the bottom of the exhaust ports. This rail connected all 4 exhaust holes together, and I believe this design was to improve exhaust scavenging. Regardless of the original engineering purpose, the 'shorty' header does not cover these additional 4 holes. It directly bolts up, but the 4 extra holes are not covered by the header. I didn't notice until after I fired my truck up the first time; it was so loud, sounded like there was no header on at all..... because there basically wasn't. I did my best to add a welded edge and put some sealer in the holes, but now i've sprung a leak and have to take it out and fix it.
2. This is the bigger issue: I am pulling a lean engine code. Plug tips are fairly white. Jumping into the details~ The 1987 EFI system used a MAP sensor instead of a MAF sensor. I guess if it was a MAF system, it would detect and automatically adjust for the improved air flow. But not with MAP. The air fuel mixture is simply a pre-programmed setting, and does not have the ability to 'read' the improved air flow. So, if my lean condition is from the header leak, then maybe I try to improve my welding job and try again to plug up the holes on the cylinder head. But if its from the improved flow of the header, I think that means I either A) Have to put the manifold back on, or B) is there a way to adjust or reprogram the air fuel mix on a MAP EFI system..?

Thoughts?
Thanks~ Dave

 

[alwaysFlOoReD]

Enough room to tap for a pipe plug?
Can't help on the fuel issue.

 

[Dirtman]

The lean code is because with a massive exhaust leak its bypassing your o2 sensor. Nothing to do with the map sensor or extra flow...

 

[alwaysFlOoReD]

Yeah, that makes sense. After the exhaust pulse goes by the hole there is a vacuum pulling in fresh air into the exhaust.

 

[Daniel Black]

You can tap those holes. They used to draw exhaust into the smog pump to go back into the intake. I had to tap the head for pipe plugs before for a long tube header. I can't remember the size plug but I think I found the info on here a few years ago.

 

[4RingCircus]

Thanks alwaysFloored and Daniel Black. The tap idea is a good one. But I had my buddy weld a lip on the bottom wedge of the header. We’ll see if this works.... keeping my fingers crossed. Otherwise the tap is going to be my next attempt.

 

[alwaysFlOoReD]

Good luck.

 

[Dirtman]

That is never going to seal...

 

[4RingCircus]

Just hooked it up and ran it. So far so good. Guess we'll see how long it lasts.