Hi, im new to vw's

, i have just got myself a golf mk4 gti turbo w reg a was hoping some of you guys could give me some help and advice on it really. I'll tell you about the car first its the 150bhp model dont know engine code though! it has 220,000 miles on it and i have service history to 160,000 verifed with vw, although i dont have any paper work after that on looking at car iv found some new parts rear springs and a few other bits, it drives fantastic boosts well drives straight, engine wise it seems fine but i think either the fan belt or tensioner wheel needs replacing as it has a slight hisss hisss hisss noise when on tickover also it sort ov ticks but you can hardly hear it been told this is just injectors, no smoke from exhaust and no loss of oil water. gearbox is tight and feels new no crunches goes into gear easily i have been told it has been replaced as it went in fifth as of high motorway miles but have no proof its the 5 speed box.
trim wise it has recaro trim and is mint except drivers bolster is starting to go but every thing else looks fantastic does not look like its done that sort of milage no worn gear knob or steering wheel only other thing on inside headcloths got a few small holes in it looks like people have had stuff in the booth and its ripped it!
body wise its not to bad it has the bbs 16 inch wheels and its in silver lots of stone chips and a few parking dents but nothing major boot handle has corroded aswel, im going to do the timing belt kit and water pump and full service but i would like any other advice tips for what you would be doing to it, i want to get a remap full stainless cat back poss intercooler and dump valve also coilovers but iv heard you need adjusterble anti roll bar link ends so help on this would be great as i drive hard lol. also any modifying tips advice most apriciated as i want to get this car split mint and a bit quicker etc cheers for the help in advance