hey mate, i think the problem is that many people stand by there modification decisions whether theyre sh1t or not.. at the end of the day you need to go and meet people, see there cars and make your own mind up.. the best place for this is meets
with any modification you make to your car, your continuously remapping the car to suit, it becomes a real nightmare so in the end you can spend alot of cash for not alot.. so really if u want a faster car your cheaper buyin a faster car.
as for the brakes, if you have brembo's then unless your a serious track whore then you wont need to change them, possibly uprate the pads, coilovers again- unless your a track whore theyre probably unnecessary, exhaust manifolds are a nightmare to change on the 350..
get yourself to some meets and have a look and see what you think for yourself.. good luck with any decisions you make