Limp Mode!

[Marc1]

I must be jinxed at the moment!

Fitted HID's and LED side lights last night after a bit of a faff with an uncompliant headlamp plug. Took the car for a drive to check out the difference and the problems started.

Filled up and restarted car - got brake warning light. Switched off and on and it was gone - put this down to the HID's or LED sidelights.
Once warmed up and after about a 30 minute spirited drive, I change to 6th gear at 4,000rpm, revs drop to 3,000 and both rev and needles stay were they are, despite accelerator increase.

I had an exhaust and remap 20 days ago and haven't driven it a massive amount since. But had noticed that when changing gear at higher revs 3,500 - 4,500 the car seemed to hesitate briefly once the revs had dropped (kind of like when ESP comes on and cuts some power). I thought this could just be me, or that the turbo was having to respool, but I'd not noticed this before the map.

Wondered what you guys thought as at the moment it could be anything, the HID is probably a red herring surely?

I thought possibly:-
MAF
Boost leak
Exhaust issue

Any ideas would be greatly appreciated, and am I right about the brake warning?

[Marc1]

Forgot to mention that the exhaust (cat back) is from a 1.8T - so petrol exhaust on a diesel car.
Could it be a lambda sensor clogged? I don't know where the sensor is, if it's in the cat, then it won't be that. Does anyone know how many lambda sensors is there and where are they?

[Marc1]

Could disconnecting the battery for 10 minutes to reset the ECU help, or am I likely to lose the new map?