Was wondering if anyone else had a car with off days?? Its a strange thing but I find my car (2.0 GT) occasionally feels sluggish and needs more revs to get any performance out of it. I know that performance is subject to so many variables and can be relative to a users exceptions but, I really do think my car is randomly more or less responsive. Its an 2009 GT that's been very well looked after and is not due a service for a few months yet. There are also days when it really surprises me as well! In a good way So, appreciate any thoughts!!
Obviously as we all know humidity can play in part of the performance of a turbo car.
In saying that I noticed the same with my 2.0Tsi. What I would say with my experience of what sounds like a similar thing to yourself is that the performance of my car has increased since I had my inlet manifold replaced a few months back, this was due to the infamous faulty flap within the manifold.
Since I had the inlet manifold replaced the performance has been much more consistent & have also seen a slight improvement in fuel economy.
I don't want to scare you in thinking that this is the issue with yours but it is coming quite a common thing on the VAG 2.0Tsi engine, as you've probably seen on the forums.
Leading up to one morning me getting the engine management light coming up to indicate an issue I had no idea other than now looking back the performance.
Thanks for the reply speccy48! Can I ask if that was an expensive fix?? Not getting any warning lights at the moment but as you say, it could be a problem brewing.....
Luckily, for me, I had extended warranty as mine's a 58 plate.
But they did tell me it would of cost about £750 all in . I believe the part alone is about £250.
Something else I've just remembered........................going back about a year previous to it going during a service they picked up an error in the memory relating to the inlet manifold but they cleared the error & it didn't come back.
Interestingly I would say the same for my TDI 170 where some days it's sluggish and almost doesn't want to go fast and on others just wants to play and go fast put it down to the turbo and weather conditions, must be days when the prevailing weather is just not suited to the turbo.
Bit of an update that hopefully someone will find helpful. My engine is clearly misfiring when its cold now. At idle, I can feel little bumps and these are also present when the car is moving and warming up. for the most part, this goes away once the engine reaches operating temp. Its pretty tedious as the Arnold Clark extended warranty I took out does not cover a £75.00 "inspection" charge which is chargeable if the mechanics cannot find a problem. Last time, they found a problem with cylinder 2 but could not pin the problem down and they didn't fix it. Must have missed that when I checked the policy. I wonder if i would invalidate my £500.00 warranty if i took it to an independent to check?
Its a strange thing but I find my car (2.0 GT) occasionally feels sluggish and needs more revs to get any performance out of it. I know that performance is subject to so many variables and can be relative to a users exceptions but, I really do think my car is randomly more or less responsive. Its an 2009 GT that's been very well looked after and is not due a service for a few months yet. There are also days when it really surprises me as well! In a good way 
. I believe the part alone is about £250.