OK
Tempted not to help you since you have some serious attitude problem but I will help you because I am NICE
Needed mods (based on upgrading to 500fps)
Laylax:
cylinder head
high pressure piston
150sp spring
trigger sear and piston sear *
spring guide
*- these are unneccisary if you purchase the Zero Trigger (highly reccomended it's AWESOME)
Those are what you NEED to get it to 500fps. Now for the mods that you will definately WANT
Firefly/ nineball hard hop rubber
6.03 or below inner barrel. 6.01 is best but you MUST use high grade ammo like digicon or SGM (if you can afford SGM)
Barrel spacers (laylax or G and G are good)
PTFE or teflon tape to get a better seal around the join between barrel and hop rubber, and around the threads of the cylinder head
If you're using heavy ammo, you will need to do the Biro tube mod (if you ask I'll link you to a site that shows you it)
Accessories that you'll probably want:
bipod
supressor
cheek pad
good quality variable mildot scope
'Gucci' Accessories:
Teflon cylinder (smoother bolt rotation ad cocking action)
Zero Trigger
aluminium precision reciever
chromed laylax hop unit
carbon fibre outer barrel
I'm pretty sure that's everything you can ever want besides a lick of paint and other minor accessories.