no idea as for clutch prices as vary from garage to garage, boost valve?? hmmmm not sure what you mean by this?? 'diverter valves' which expell turbo pressure from the system on throttle of situations can be upgraded to dump valves which make a nice noise!!, or if your on about upping boost (turbo) the old fashioned way was to get a bleed valve to fool the waste gate into opening up lter there fore giving more boost but i wouldnt go this route as you could just get a chip/remap which will alter stuff and make alot quicker any way (bleed valves not very accurate have poppped a few rs turbos in me time winding em too far open!!),not sure of upgrading air/mass meter, theres a few new mk4 member with some seriously modded/tuned turbo cars may there worth having a word with!! if you bump into 'snowball' hes got a mega lump and im sure hed know if poss to mod them!
