Fuck. I knew you'd ask that.

Well to start with if you've got a 2wd exhaust manifold, you'll need to replace the trousers with something like the item Martin at Reyland sells for, IIRC, £288 to mount the wastegate on. Then you'd have to make up the screamer pipe. Then you'd probably have to have the boost control checked/adjusted. Then you'll find that you're no better off than what you were running previously. Apart from you're skint.

You really don't need one unless you've got a turbo without an internal wastegate eg a GT30 (although you can get a version of this that does have an internal wastegate so you still won't need one)