I'm facing aparently a similar issue, but not sure it's the MAF.
I was to reflash my 996 C2 (MY2000) and first found max power was at 277 hp instead of the expected over 300 (bypass, gt3 throttle body, ipd plenum, bmc air filter...).
Then the guy checking the numbers found too lean mix at higher rpm which I did not expect as car was running perfect IMO. Anyhow we postponed the reflash till the lean issue was solved.
See the dyno bellow:
[IMG]
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SInce this test last week I've clean the MAF, checked for leakages and read a LOT of posts about it but still could not get a clear idea. Since I have a durametric cable I did a couple tests on 3rd gear WOT a recorded the following parameters:
1-RPM
2-Mass air flow (MAF)
3-Adaption, range 2 (FRA), bank 1
4-Adaption, range 1 (RKAT), bank 1
5-O2 sensor voltage ahead of cat. conv., bank 1
6-Adaption, range 2 (FRA), bank 2
7-Adaption, range 1 (RKAT), bank 2
8-O2 sensor voltage ahead of cat. conv., bank 2
1 2 3 4 5 6 7 8
1.681 160 1,02 -0,19 0,84 1 -0,52 0,87
1.928 188 1,02 -0,19 0,88 1 -0,52 0,88
2.176 221 1,02 -0,19 0,86 1 -0,52 0,87
2.418 237 1,02 -0,19 0,88 1 -0,52 0,88
2.673 244 1 -0,19 0,88 1 -0,52 0,89
2.921 295 1 -0,19 0,88 1 -0,52 0,87
3.156 323 1 -0,19 0,87 1 -0,52 0,86
3.400 342 1 -0,19 0,88 1 -0,52 0,88
3.679 390 1 -0,19 0,87 1 -0,52 0,87
3.985 437 1 -0,19 0,87 1 -0,52 0,88
4.253 468 1 -0,19 0,87 1 -0,52 0,87
4.539 516 1 -0,19 0,87 1 -0,52 0,86
4.816 561 1 -0,19 0,86 1 -0,52 0,86
5.104 589 1 -0,19 0,85 1 -0,52 0,85
5.424 624 1 -0,19 0,84 1 -0,52 0,84
5.697 667 1 -0,19 0,84 1 -0,52 0,83
5.988 695 1 -0,19 0,83 1 -0,52 0,83
6.286 680 1 -0,19 0,81 1 -0,52 0,81
6.565 704 1 -0,19 0,81 1 -0,52 0,76
6.857 764 1 -0,19 0,83 1 -0,52 0,82
7.056 784 1 -0,19 0,85 1 -0,52 0,83
7.306 643 1 -0,19 0,84 1 -0,52 0,81
Any clues?
Thanks in advance