I put a set of 4-1 on my GZE and seemed to open up the top end a bit . Not sure what they were made for but I think they were just new 4AGE "Rage"?? extractors for 16V..
Doesn't really help you does it...........
NZ AE82 GL Liftback Tarmac Rally spec NZ AE82 GT Liftback x 2 R32 Skyline GTS-t Type M Coupe '07 Subaru Legacy GTB '03 Runx 2ZZ-GE 6spd