cant change an internal spring, but you can run a boost controller. dont need an egt., but i would rcommend a wideband, i wished i would have gotten one, soon tho. as far as internal vs. external, external in my opnion is much better for high power applications and if you want to adjust your boost without dicking around with a boost controller, not to mention they look cool as hell. internal gates are excellent for lower applications, thats what i have for my d, but i will be switching to external when i go dohc with my fatty turbo.
for injectors, your gonna want something that will have room for mods, 450s on a dohc isnt bad, but limits you. im gona be shooting for the 450-500 range so im going with 1000cc injectors, some say over kill, but there 10 bux more and i wont ever need to worry about maxing them out.
fuel management ranges from fmu, very, very bad. to moded ecu to hondata or aem. if i were you, i would look into either crome, neptune or uberdata, all very nice, but crome pro has an auto tune feature, very nice.