the GTS is the one that does not have any good aftermarket headers...although the 1zz (GT) seems to benifit from the hotshot and DC header...
the problem really has to do with how wide the collectors are. the collectors are just a little wider than optimum on otherwise stock car (or with any type of CAI
or shortram). with higher compression pistons and/or cams the aftermarket headers like dc, trial, and TRD
will work a lot better than stock.
i drop my engine off tomorrow for a port job as well as higher compression pistons (among other things). i'll be installing my dc-s header and it'll be dyno'd so i'll let you guys know whats up (not on this site of course ha).