Well, got the ecu upgrade, & the difference on my Mk1 is very impressive!! :smt003 .
Throttle response is excellent, smoother pick up, more mid range & much better top end (revs easily to 7k). I can't believe the difference. The car will pull in 5th from 1000rpm, without hesitation at all. Not sure how much power it really gives, but from a drivability point of view its fantastic. With my exhaust & bmc kit, they've tailored the ecu for my engine & done a top job.
I'm gonna try & get it on a rolling road soon, & see how much i've got. If you've got a spare few hundred pounds, go to DMS.