flat running on 2.7 986 2000MY

[HairyPotter]

My 2000 2.7 feels like it's running as flat as a pancake. I've recently replaced the MAF and thought it might be poor quality or faulty but it made no discernible difference when I disconnected it and took it for a 5 mile run. The car has an electronic throttle and idles evenly at just over 600 rpm on the tacho.

I changed all the spark plugs (checked for correct grade) and coil packs approx 12 months / 5,000 miles ago. When I fitted the new MAF I took the opportunity to clean out the throttle body and air intake system as I previously changed the AOS due to failure. I have remade every join in the air intake system to make absolutely certain that additional unmetered air isn't getting in. I even swapped the exhaust headers back to standard but this seems to have made the situation slightly worse if anything (at least now I think the headers are better than OE).

The air filter (OE) is as new, no CEL, all the visible vacuum pipes, electrical connectors, etc are connected and intact and draw through the oil filler cap is fine (not too strong). I have coasted the car from speed in gear and in neutral so I don't think it's unwanted friction in the brakes or drivetrain. I usually run it on BP Ultimate fuel.

I'm thinking fuel delivery or pressure - possibly a partly blocked fuel filter.

Anybody got any further suggestions?

[RFM]

Check also under the air filter element (air filter housing) for debris like leafs, which disturbs the air flow to the MAF, blow out the housing with compressed air. Critical point on a 986, you cant see inside the housing without a mirror.

[dr914jr]

Get someone with durametric software to monitor the o2 values as you drive. That's about the best way to see if you're running lean. However I sure do think that would cause a CEL but it's entirely passable that you're just on the limit.

[HairyPotter]

Check also under the air filter element (air filter housing) for debris like leafs, which disturbs the air flow to the MAF, blow out the housing with compressed air. Critical point on a 986, you cant see inside the housing without a mirror.

did that as well, cheers for the suggestion though

[HairyPotter]

Get someone with durametric software to monitor the o2 values as you drive. That's about the best way to see if you're running lean. However I sure do think that would cause a CEL but it's entirely passable that you're just on the limit.

good idea - my neighbour plugged his new durametric in yesterday while I was putting the sport headers back on and no faults were stored - I'll get him to bring it along for a drive