top speed problem, maf??

[arnoldlog1]

i've got a gt tdi 130(2002), it's great had it a couple of years now love it, but i've noticed i seem to have a top end speed problem. when i first had my car my car would accelerate really well to about 120mph, (on a private road of course officer!) but now i get to about 100mph and i really struggle to get it up any higher. I've got no other issues with the car my mpg is great, i average 50 ish, no fault codes.

any ideas? i was thinking could be maf but i though i would see a difference in every gear, and i can't, thought it might be wheel alignment but i get no vibration from the steering wheel, and i get even tyre wear.

any ideas?

[Rhyso]

when was it last serviced?

dodgy MAF normally results in worsening MPG; does it feel flat at any point in the rev range?

have you checked for air leaks etc and you could be loosing pressure albeit in tiny amounts

[arnoldlog1]

no thats what i can't work out it's not flat at all, it revs really well no flat spots. mpg is fine if anything getting better mpg now(maybe i don't drive it as hard as when i first had it).
it was last serviced 3.5k ago by my local vw specialist.
had a check round no signs of any air leaks.

[caddy vantastic]

Possible Map sensor fault. That causes the same effects you are having.

[arnoldlog1]

can anyone explain what a map sensor is? and more importantly what it does?

[Rhyso]

this thread may help??

http://uk-mkivs.net/forums/thread/1062710.aspx