Need 2nd opinion on P1128 mass air flow sensor diagnosis

[Douge1]

Hey everybody, my girlfriend is selling her 2000 986 S and it is throwing a CEL It is a P1128. I can defeat it with an OBDII but it comes back after a few drive cycles and has a very noticeable flat spot around 4500-5000 R's with 50% throttle and above. Additionally the idle sporadically revs +3-400 r's when stopped. Car runs and drives very well in lower R's and you wouldn't even know it had an issue. I opened it up and hosed down the MAS with MAS cleaner and it did not cure it but the air filter was pretty dirty and she couldn't remember last time it had been replaced. The car has 56000 miles on the clock.

Thanks for any help

Doug