If I calculate the % of boost compared to the percentage of gain that's a fair assumption (obviously cams and headers are there to facilitate/compensate for the increced flow)
And in my performance book 1 horsepower per $50 ex vat is still a [s]good[/s]acceptable deal for na->fi conversions, so the allowable cost for this mod should be about $160 (about €180 where I live incl taxes). So with the TB bought for €30 I still have 150 left to tinker
I have no idea if it will really make a 3hp difference, but these simple calculations show that a 15HP difference or so often claimed by parties who sell big bore TB's and whatnot is not very likely (and the calculations I did were on a boosted engine, so more flow/loss going through than NA/stock....). Somehow advertized claims are never underrated....
Dinan attributes 6hp to their TB, and I think that's also largely overrated. Certainly regarding that their TB is much much smaller than the diameter we used in the calulations in this thread, and their spec in on a NA car too.