PD130 boost pipe upgrade and maintenance

In the coming days I shall be crawling under my car to examine the boost pipes. The reason for this is that I am sure I have some kind of boost leak because when accelerating there is a low pitch air escaping noise that also sounds a bit like a constant rubbing sound. Hard to describe. As well as this the car averages about 34mpg. My friends mk4 golf with same engine gets around 45mpg and his is nice and quiet.

So I will be checking for anything loose etc. Also, I remeber when last under there some pipes had oil on them, and I do have a small oil leak, so this is where I will be first looking.

My question is, is there any pipes or joint I should replace anyway to increase performance or to make more secure as I know some of VAG pipe joints can be crap. One other thing. Is there anything else I could look for whilst under there?