Modifications to the stock BOV is not the best way to go. If you remove the plum back it will leak boost, if you remove it then you will have al your boost going back through the turbo.
some cars come like this from factory (some supra models inclusive) so its not the worst thing, I have a aftermarket BOV which I have set to not open at low boost. (hence i get the phew phew phew noise but at full boost the BOV opens and does its bit.
It will slightly decrease the life of your turbo, so i recomend at full boost you have a proper BOV.
Also the stock computer will not adjust for life with out the Bov. It will run rich when your bov goes, and you will get a little bit of back fire. This is normal, and if you want it to go away change your computer.
ps.. Cant wait to get out to the track, remove my cat and see what flamage I get..