The 2 different plugs ia on the ZX2 for sure. It seems to me you're right thought and IIRC it has to do with the VCT on the 98's and up.
Green 96 mystique gs 4cyl mtx
16.9 in the 1/4 mile @102500 miles
95SE in Midnight Red MTX
MSDS headers and y-pipe
SVT exhaust
SVT UIM
Optimized se TB.
Full pre 98 SVT body kit
15.741 @ 87.73mph :)
