The celica isn't meant for straights... if thats what your after.. but..
get a APEXi Power FC Engine Management ECU
that's the way to go POWER FC, it will get you in high 13's with it alone. well with very good tune.
there is also headers, stroker kit(2000cc), piston from TRD
, Flywheel(helps a lot), LSD, clutch(ofcourse), better tires, gear ratio from c-one.
Belive it or not there are lot of parts for celica, they are just too damn expensive.
And also HP number isn't all about how fast it is. Its all about your drive-train.
and how well you drive.