For some reason when maintaining an average speed as soon as I drop a gear and floor it to overtake on the motorway it stutters but eventually accelerates?

Any idea why?

Most posts of searches say its the MAF or Filter but so far I have changed the MAF, Air Filter, and had the turbo valve cleaned out and it had 120K service a few thousand miles back and passed MOT last week with no problem so not sure what else it could be?

 

Sounds like coil pack or maybe plugs to me

 

coil packs/pack plug gaps

 

I had these same symptoms. Turned out to be a cracked ringland.
I recommend you get it compression tested before anything else

 

Only the 2.5s suffered ringland probs
Dont think the op car is a 2.5?

 

It's a year 2000 classic turbo wagon if that helps. Only Mods it has is a decat centre pipe leaving the front de-cat and Pipercross filter but it did have an episode where the engine got VERY hot when the raditor split last year.

I had a diagnostic check done at Subaru 4 You a few weeks back should that not flaged up if there was a problem with plugs/coil?

Oddly enough the stutter only happens in 3rd & 4th?

Also where is the best place to buy coil pack and plugs since they seem to vairy in price everywhre you look.

 

IMHO a slight hesitation when flooring it is quite normal you are suddenly opening the throttle far wider than the engine can utilise at that point.

I drove a brand new car on a test drive before i bought mine and it did the same thing, no doubt it can be accomodated for in the map but out of the box the 2005STi for example did hesitate if you suddenly floored it when it was off cam / boost.

 

Agreed!
Standard maps are a bit ****e.

 

Odd that it never seemed to do it before?
I have orderd some new plugs and see it that helps.

 

Well just got the car back from garage £140 less in the wallet but turns out the leads where knackered and one fell apart while they tried to get to the plugs. So that's new plugs and new leads so hopefully that will solve the stuttering.