i bought my GT28R for about £400 but got hit for £100 on tax.

Apex Performance sell them fro about £550 in this country, good price.

on my 1.8 i am seeing boost from low down < 2000rpm probably (not really looked). i hit full boost by 3,500rpm (give or take a few hundred). i'm running 18psi and should be at about 300bhp.

one thing though, the GT28R doesn't seem to want to hold to the 7,200rpm redline and there are a few people with different specs who run one on a CA18DET, all of us seem to have 16psi by the redline. (some people have big FMIC's, electronic boost control, etc - the one common factor is Mongoose exhausts, maybe they are restricting us all.)

i think the GT28RS is probably a better option than the R (the smaller RS - 350bhp one)