40-50K a year, sheesh, I thought I had it bad at 20K commuting a year
MK5s make for great daily drivers and are cheap and easy to fix, aside from the big stuff like gearboxes and turbos, but that's common to all cars.
Don't bother with hardware, just get a Stage 1 remap. Wakes up the car somewhere close to it's max potential without breaking the bank. A remapped GTI/ED30 can still keep up with current hot hatches, so you're not losing out much there. Focus more on the suspension as that is one area that really brings them alive on B roads. It's a VERY stiff bodyshell for VWs of the period, so lends itself well to chassis mods.
The golfgti forum has been around for years and can be a cold to newbies. This place is one of the easiest going, friendliest forums I've used to date
My mate is currently putting a 1.9 Golf TDI engine into his MK3 MR2. Should make an interesting little project in such a light car!