second 0-400m drag time

so i went to calder park again to try out my new mods:
AEM CAI, Magnaflow catback, take off the rear seats

i did 15.6sec @ 89mph on that day...

very disappointing for me but i guess i need vtec also need to use 17inch.... coz i think the 18 inch also affect the time... (its a common excuse for a slow poke )