I think they are quite quick when driven properly. They grip well, have good brakes and the engines are bomb proof. Maybe you just can't drive
ABf in a mk2 is the compromise, just like mine! It got an indicated 140mph (private road ossifer) and had plenty left in it.
You must have driven a dud IMHO, granted you do have to rev them up past 4k, but when you do they really shift. Standard they are 150bhp, mine is doing 164bhp last time it was RR`d(before the Jetex). My previous Mk2 valver was about the same, although I think the Mk3 is actually a bit more eager to rev. Drive another, and rev the bugger!
Couldn't find it, it must've ended; was a nice car, though, had all the Seat interior and even a swap to cable change (why you'd bother, I don't know, but anyway...)