Wastegate woes - please help

[Lum]

Aftet getting fed up of waiting for a new spring for my HKS wastegate i decided to buy a new wastegate. Due to running out of money i went for a cheap one from xs power, it\'s basically an exact copy of the HKS one i have.
Ordered a 40mm one, recieved it yesterday and fitted it last nite thinking that would be the end of it!
Wrong! couldn\'t understand why i was gettin quite bad boost spike? Spring is 11psi.
So i took it off again to investigate.
Turns out the inlet on the bottom is 40mm, no probs there. However the outlet for plumbing back to exhaust or screamer pipe only measures 31mm!
This is restricting the flow, effectivly making it a 31mm wastegate!
Surely this can\'t be right can it? I\'ve sent an email to xs power explaining the problem and requesting a refund.
What do you think? Am i right to ask for a refund? Surely to be a 40mm wastegate it should be 40mm all the way through?