Is this limp mode??

[fasttdi]

A4 TDI 2004 .... Good evening, I was driving my car last night joining the M5 motorway, I had to floor it because there was a truck beside me. Any way I was in 3rd gear and floored it to about 4500 rpm before i changed into fourth (i Know i shouldnt have but felt the urge!)
I noticed as i reached 4500 rpm the engine suddenly lost its turbo boost and i instantly thought i had blown my turbo. there was no smoke visible and maybe out of fear i may have damaged somthing i slowed right down to 40, if i tried to accellerate it felt as if it wants to go but something is pulling it back.

I drove up to the next junction and had a scan under the bonnet to see if i could see anything obvious, but nothing. I then started the car and to my suprise it drove fine.

I feel ive had an issue with the turbo overboosting, not too sure but car makes a grinding noise whilst driving at low speeds... 1st, 2nd and 3rd gear upto 40mph.

Ive recently 100miles ago had my timing belt kit changed, could the timing be too far advanced? as ive noticed the engine noise to be louder at 2500rpm onwards. the reason why i say this is, i walked into the garage whilst my timing was being done and realised the top engine cover or rocket cover had'nt been removed, i may be wrong but to my understanding i thought the pins had to be locked in from the back end of the engine for correct timing.

[fasttdi]

anyone???