High BLMs vs. Cracked Header vs. Fuel Pressure

[BASS]

OK, assuming that I have a good MAF, good O2 sensor, no vacuum leaks, and no exhaust leaks, would raising the static fuel pressure lower or higher the idle BLMs??

Now, the same question---If everything above remains the same, EXCEPT that I have a header leak, would raising the fuel pressure lower or higher the idle BLM???

Heres my story--I had a bad MAF sensor (the AF never made it to 255 @ WOT, and it would drop down to 180 during WOT still), and to somehow make the car not knock, I raised the static fuel pressure to approx. 60 psi static (line off) and the car ran ok. During this time, my idle BLM was 128.

Now, fast forward to today---I installed another MAF (a good one this time) and it hits 255 and remains at 255 @ WOT. So, I lowered the static fuel pressure to the suggested 43 psi static (line off), and now I noticed that my idle BLM rose to 140. From the start, I think I have a cracked driver-side header, and it just got worse im thinking since ive been doing all this WOT testing today with my car since i installed my new MAF. Im also getting random knock @ top of third/4th gear (about 2-9 degrees), and im thinking its the exhaust leak???? I do hear a slight ticking noise coming from the driver side, and its not coming from the bottom end or under the valve cover, so Im thinking it must be the damn header (I had it recently welded though)...

Could it be possible that I fouled up the O2 sensor and my spark plugs from running soooo rich the past couple weeks?? And maybe thats why my idle BLM went up now since I adjusted the static fuel pressure to the correct (lowered) pressure????? Or do you think its an actual exhaust leak causing this high idle BLM?? I have a TT 93 chip by the way burned for MSD 50's and a stock turbo....

 

[ijames]

What times/mph do you run? You actually need to be somewhere in the mid-13's before the MAF should be maxed out the entire pass. Raising the fuel pressure lowers the blms. An exhaust leak will USUALLY suck in air at idle and make the O2 sensor think the engine is lean so the ecm raises the blm to add more fuel so the engine winds up rich. Somewhere just above idle, especially in gear, there is enough flow/pressure in the exhaust to blow exhaust out of the leak instead, and the O2 will read correctly. That's why an exhaust leak will usually make the idle blm 150+ but not change the cruise cells. An exhaust leak shouldn't cause knock, especially at the top end. Have you ever put leaded race gas in? What are the O2 readings as you pull through 3rd gear, are they steady or do they jump up and down or slowly drift up or down as the rpm rises?