MAF values on an 02 Boxster S
 

Ok here is the situation.
Last week, on the highway, when i stepped hard on the throttle, I got some major engine stall, and a hint of misfires, as if i was running on really bad petrol, but i had filled my car up 3 days ago and never felt anything before then.
When I caught up with the traffic ahead, and had to stop the car, the engine stopped running.
I fired it up again, and it never gave me any problems again, neither stalls, nor any problems at idle.

I never got any CEL warning.

I called my garage (former porsche chief mechanic), he said it was probably the MAF, but could otherwise be the alternator.

Today, i went to check it at the garage, still no CEL. The reader indicated trouble with the MAF, which gave values of 13-16, a couple of times 17, at idle. Before he connected the laptop, he said it should read higher than 18.

Keep in mind, I have a Revo chip, a BMC free flow air filter and a sport exhaust.

After I replaced the exhaust, i was getting a not so smooth idle, ranging from 600-900 RPMs. But after 10 days, it smoothed out, so now it's good as new.

I wouldn't go to check it, because i dont have any indication there is anything wrong at the moment, but ever since that day i got stalls, Im getting the impression that my car is not performing as well as it did, but this could just be my imagination. The mechanic who drove it for a bit today, said it runs awesome after he cleaned the MAF sensor. The reading was still below 17 even after cleaning it.

So the question is this, how can i tell if i have a faulty MAF sensor? The idle is smooth, i get no misfires or stalls, and the only hint there might be something wrong is the fact the car might not be as fast as it did, but i could be wrong and just imagining stuff.
Im asking all this because i don't wanna pay the 400 Euro ticket to get a new MAF, if I don't have to.

Please help...

Cheers,
Alex

PS: Is there an aftermarket MAF for my 2002 boxster S? I read somewhere it uses a Bosch sensor, that is also for sale as an aftermarket part for less than half the money and it's the exact same part Porsche uses for its cars, but I cannot find the thread, nor can i have this confirmed.