HELP!! Power Loss - GTI MKIV 1.8T

I have a '02 GTI MKIV 1.8T which has been driving beautifully with a Boost controller for the past 3 yrs. Recently on a long trip I developed an overheating problem and since then my power levels seem to have gone down considerably. Sometimes between 1,000 to 2,500 rpms there is very little power and flooring the pedal results in no change and it will take several seconds (much longer than normal turbo lag) before it accelerates. During this time the car feels as if nothing is happening in the combustion chambers. Occasionally it stalls.

However, once I can get the revs up to say 3500 rpms, it will accelarate and even at this level the usual zip seems to be missing.

Any suggestions anyone.

Zicketts

What caused the overheating issue? Was it fixed?
I would check the bypass valve, its a common failure on boosted 1.8t get a baileys or forge diverter valve