[Tygen1]

So, this thread is in reference another thread I made in "Success Stories" where it seemed that changing my accessory pullies out suddenly gave me better mpg. However I found an unpluged line on my intake tube that was letting unmetered air in... Well, since I've plugged it back in my mpg has droped. My typical mpg reading at 50mph was mid to high fifties, now it's mid to high fourties. Maybe the ECM messed with the long term fuel trims when the leak was happening? So after getting a couple consistant commutes to see what the current mpg was, I found I was getting high thirties and maybe touching on fourty mpg by the time I got to work. This morning I unpluged the hose to see what would happen and I imediatly noticed a big change. In fact I was at 50.3 mpg when I got to work this morning and the mpg at 50mph was high fifties, low sixties.
To be clear, this is a hose which plugs into the intake tube between the MAF and Throttle Body. MPG before unplugging the hose was high forties on the way to work, after being unplugged it jumped up to high forties, low fifties, after pluging it back in it dropped to high thirties low forties. Now after unplugging is again it's high forties low fifties.
Does anybody have a clue why this is happening?
I don't imagine my SG is being fooled. I figured the ECM would just see what's happening at the O2 sensor and compensate if things were lean? Speaking of lean, I get a little ping when acclerating with this hose unplugged, so I am guessing it's a bit lean.