I would PM you, but this info could be useful to others, so I'll post it here.
The upgrades can be found on:
You specifically want:
Cylinder head: http://airsoftpro.cz/eshop/product_i...oducts_id=2231
New hop up unit (works GREAT, the stock hop-up unit is crap and double feeds all the time): http://airsoftpro.cz/eshop/product_i...oducts_id=1814
Aluminum and steel piston: http://airsoftpro.cz/eshop/product_i...oducts_id=1473
Steel sear: http://airsoftpro.cz/eshop/product_i...roducts_id=821
Stable outer barrel housing: http://airsoftpro.cz/eshop/product_i...oducts_id=2484
The stock piston is not bad, but the upgraded piston will last longer with the upgraded sear and allows you to use a AEG piston head, such as a Prometheus or ARS piston heads, which are great and seal very well.
I've found the inner barrel to be pretty decent once it is cleaned thoroughly, I did not get much more precision from upgrading to a Prometheus barrel, so it is not a priority upgrade if you are short on funds.
You will also want a good hop up rubber, any AEG rubber will work, use your preffered brand.
I would suggest you read this whole thread, it's full of great info: