The heads flow differently in 05 and 06 vs 07+.. perhaps they realized less timing (on a stock setup) could be achieved with the higher flow of the B25 heads...?
go to the dealer and buy 5 qts of ATF-HP for the tranny. its 5eat atf, the 4eat tranny uses diff fluid so make sure it says HP on the bottle(silver bottles). diff fluid is 70w-90, i use mobil 1 or valvoline, really anything thats GL-5 rated is fine.
diff fluid is its own compartment and so is atf fluid. you fill atf through the tranny dipstick tube. use a funnel with a long flex tube. it might take a while but thats how you fill the tranny. no other way.
it is HIGHLY advisable to use the same year transmission as the car. one member tried using an 05 5eat in an 06 and failed due to electronic gremlins. you certainly cannot use an 08-09 tranny in a previous year.
this has been debated too many times.
some people have blown their tranny's with a 16g at just around 300hp, others have been fine running 320hp with a 20g.... though sprank is the only one i know of that blew a tranny with a 16g....