Hi Guys
Last week I purchased (privately) a 1999 996 tip. It was serviced by an indy 3 weeks ago.
I have not driven the car much as the seller was very local.

I spent last weekend giving it a good clean but soon after a fault developed. With 2 minutes of driving the car started feeling down on power and 'stuttery'. If you applied the throtle when stationary it sounds stuttery and not right at all. The EML light came on.

I thought it may be the MAF? I disconnected the battery and removed the MAF and attempted to clean the terminals. I replaced it and re-connected the battery.

The EML light did not come back on when I re-started.

From cold the car runs fine. As soon as its driven for more than 1-2 minutes the problem resppears.

Any suggestions??

Cheers

Heat related? Maybe something as simple as a poor connection to a sensor going open circuit as the car gets hot.

Not a 911, but my Alp currently has this problem, the tricky bit is finding out which sensor

It depends on the type of service carried out.

sounds like misfires, take it back to the indy that did the last service for diag. Could be any number of things.

when my coil packs began to fail the read out on the dash identified it was No. 6 cylinder. I bought a cheap decoder which confirmed it. 6 new coil packs later and job done. Could be plugs. I notice it's a tiptronic, would it be teaching my GM to say you do know that it has a rev limiter which cuts in if you rev a tiptronic car in neutral?

A good wash you say, followed by engine running rough, sounds like cracked coil pack(s) and water ingress.

I had a similar problem when I first bought my 996. Luckily for me I bought it off a dealer and it was covered under warranty. All plugs were changed in the service before I bought it, and the one on cylinder 6 was replaced again in case it was faulty. Issue arose again. Then all coil packs were changed, but the issue raised it's head again.
Finally a Porsche Indy here diagnosed a faulty tappet sticking open causing the misfire in cylinder 6. So, it was an engine out job. Cost the dealer nearly €5000 to sort. I hope this isn't what you have.
My car has run perfectly ever since.
Maybe try moving a plug from cylinder 6 to a different one and move the coil from 6 to another also. See if the misfire arises again in 6 or one of the others. At least that'll rule out or prove a plug or coil.

Goodluck.