A TBB is usually a good idea for extra power and accuracy, but maybe you should chrono your gun with those upgrades and see how close to your local site's FPS limit it is. That is a good bunch of stuff to get for £40, but if you're going to break your gearbox down, i'd choose bearings rather than bushings - Kanzen if you can afford them. Also get some Guarder Teflon Grease - clean the stock grease off and lube up every moving part's contact surfaces with plenty of the new stuff.
Depending on air seals, you could get just over 350FPS with a P90 length barrel and a 110 spring - a TBB may boost that enough that you could run a 100 spring instead and chrono @345-ish, which would increase the longevity of your parts. I know someone who has a P90 with frighteningly impressive range but, that said, I've only seen it at a woodland site with a 368FPS hard limit, so he may well be running it too hot for most sites.
Oh, and remember that if you add a longer tight bore barrel inside a suppressor you will increase your FPS more than with a stock length one.
& i can't not add - they are such pig ugly guns: have you considered just selling it to someone with no taste for a profit?
