Anybody had an up-pipe fitted to their scooby (not a down pipe) and if so does it make a difference??

 

Yes mate, quite a few people have done so. The benefits you would find will depend on the spec of your own car. Some models have a cat in the original up-pipe, and some don't. If you replace a catted up-pipe with a straight-through one, there will be benefits. If your car doesn't have a catted up-pipe, there's less benefit. You might still find some gains though.

What model is your car?