I'm not a novice LNF owner. I've had the car for 3.5 years. I've serviced it myself. I've upgraded it. I know what I'm doing. I know how the car has ran/is supposed to run. I'm not some kid who picked it up and has no idea wtf they're doing.
I know how to calc mileage. I know what my mileage has been. And 23 CALCULATED on highway driving means that something is wrong.

 

Next thing on the list is walnut blasting those valves. Maybe run some seafoam through the gas tank couldn't hurt.

 

any luck with a vacuum leak?

 

No luck yet but I haven't had a real chance to sit down and dig into her. I'm gonna clean my MAF and see if that makes any change (even though I'm nearly positive there's a leak somewhere. I unplugged the MAF and it didn't run any different so I'm gonna try that.
Hopefully can get my car up on the lift this weekend and see what's up

 

Update: seafoamed, changed the oil and put a fresh set of plugs in her. No change. Fuel trims went WAY out of whack (-15 to -25). Runs no better than it did prior.

Current symptoms:
Won't boost past 21PSI.
Vacuum is -16.7in Hg at idle
Occasionally (ONLY occasionally) if I coast in neutral at a high speed (above 40mph), it'll dip down to 200-300RPM and nearly die
STFT regularly ranges from -5 to -15. Occasionally it'll read +10 (really doesn't stay positive though), and has seen as bad as -28)
FTFT is -6 to -10 regularly
Wideband O2 is going out - when cruising, it'll ease it's way down to .70 LAMBDA before shooting back up to 1.00 where it should be

Car has no CELs. And it hasn't had one. I check occasionally with my Interceptor to see if there's any hidden codes, and there isn't.