Chasing vacuum leaks and goes no where

[theWalkinator]

Originally Posted by AK986

Hey, i'm running in to the similar issue with my 98 Boxster. I checked the car for vacuum leaks by using the smoke detector ,and couldn't not find any.

Any updates on your progress?

I replaced vacuum reservoir and that helped to get rid of P1128 and P1130 (idle below limit) codes, but P1126 and P1133 (lower range exceed limit) codes still present.

I also replaced fuel filter which is really dirty (fuel came out of the filter is cloudy and contains fine black sediments), after replaced fuel filter, I re-checked the fuel pressure, idle at 3.3bar which is right on the spec, but engine off fuel pressure is kept at 3.5bar which is 0.3 bar lower than the spec, but I don't think it really matters. Also replaced the spark plugs with NGK Iridium plugs as well as spark plug tubes since they are leaking oil and might also leaking vacuum, but all that didn't resolve P1126 and P1133 codes.

Other things checked:
1. Checked vacuum at the Y hose connector, it holds vacuum
2. Fuel regulator, pulled out the small vacuum hose from the fuel regulator, it is dry no fuel came out, the small vacuum hose has suction so both fuel regulator and vacuum are good.
3. Checked EVAP purge valve with my scanner and a hand vacuum pump, I can command the valve open and close, when it is closed, it holds the vacuum but when I command it open, the vacuum drops to 0 so that ruled out the EVAP purge valve.

I also tried with the MAF plug disconnected, P1126 and P1133 codes did not show after 10 miles test drive, so at this point I think most likely it is the wrong MAF sensor that I bought from RockAuto which is 98660612502, though all online sellers (FCP Euro, Pelican Parts, RockAuto, etc.) give this MAF sensor as the correct one for my car, but the original MAF sensor in the car is Bosch F00C2G2064, I couldn't find anywhere that this MAF sensor fits my car or any boxster, except one eBay seller who has a list of Bosch 99660612400 but the item picture shows Bosch F00C2G2063. My car is 2001 2.7L but the production date is in Sept 2000 so 99660612400 might be the correct MAF sensor for my car, this website https://www.eurospares.co.uk/Porsche/Boxster_986/Boxster_986_(2001)/PartDiagrams/106-000/AIR_CLEANER?ref=7 listed both 99660612400 and 98660612500 fit 2001 boxster 2.7L.

If 99660612400 won't resolve the P1126 and P1133 then the last thing is the fuel pump?