Make sure your Mk5 GTI is running how it should, its pointless spending money elsewhere till its running sweet.
Dont forget to check your
Cam Follower on a moded engine it will wear down so much faster you should check it every 5k/10k miles just to make sure, if it goes it can be ££££££s on repairs.
So down to the mods.
There are countless aesthetic mods you can do pointless listing just have a good search and i am sure you will find some stuff you will like.
You can go for a
stage 1 remap without doing any moding to your car if you want although having some mods wil aid in better figures and delivery of the power to the road.
R-Tech Performance are one of if not the best in the UK.
The main engine mods people seam to do are =
Air filter - You can go for a number of different choices to open air system where it will take air in from inside the engine bay normally near the battery useing a heat shield or to a closed air system that will take air from outside the engine bay from one of your many grills.
High Pressure Fuel Pump - The Golf uses a HPFP and when taking the car to higher power levels it just dosent cut the mustard you can get an internals kit from a number of places that will boost the performance of the HPFP and help you hit those tasty numbers. Normally around £400.
Full SS Exhaust System Turbo Back - This is something that can be a big ticket item if going for the full turbo back exhaust where you will get performance and also sound there are hundreds of places where they will fabricate you one or you can also get one off the shelf go for a 3inch system.
Although a full turbo back is not necessary the stock downpipe and cat are very restrictive with air flow so you could just go for a 3inch downpipe and decat/sports cat useing an exhaust reducer to connect it upto the stock cat back exhaust. (With new MOT regulations unless you know a friendly MOT place you wont get it through with a decat you will have to pull of the decat and re attach your cat)
Diverter valve - The earlier revision will break alot, it has a rubber skirt on ther piston and this tends to tears. You can upgrade it to a newer revision thats plastic for around £50 or you can go for a much more solid metal design there are a few out there but i went with a
GFB DV+ as they had a lot of people giving them amazing reviews.
Now if you are going to go for more power dont forget some
good tyres and to sort out your
brakes there are 100s of different ways you can increase stopping power but its a must when chasing numbers.. unless you want to go hug sometrees
Also an
anti lift kit and
anti roll bars are just a couple of the many good ideas to help you put the power down and turn corners.