Flat throttle response on pull away 2.5 Boxster S
 

I have a 1999 2.5 Boxster S Tip. Owned for 1 year Just turned 60K and due a service. Had an air filter about 1K miles back. Fuel economy about 30 MPG (UK) on a run.

Its had this engine 'dying' problem showing up over the last few months.
OK start the car - no problems and tick over is fine and steady. Get the engine up to temperature, performance seems ok but not powerful or that torquey(have not driven one before maybe expecting too much from 2.5).
Sitting in stationary traffic for a few minuets or at the lights or worse stopped and needing to turn across on-coming traffic the engine almost stalls on normal throttle depression, then picks up sluggishly and away.

There is no engine light on.

Please can someone suggest the best plan to track down the likely cause. Have read about sensors and fault codes but what should I look at first?

FYI: Porsche did not build a 99 Boxster "S" model as far as I know. The 2.5 cars were all Base models with a 3.2L "S" available in 2000.

As for your sluggish performance, a failing MAF is the most common cause. It will degrade performance well before tripping a check engine light. If you unplug the MAF and your car runs better, clean or replace your MAF.

the first thing I would do is check the air filter, a little dirt and they don't want to go. then the maf and lastly the fuel filter, a lot of people forget about the fuel filter under the center panel under the car and topless is right the first S came out in 2000 with a 3.2 liter engine