Okay, I tried to go through your post to try to understand it a bit more, but I'm still sort of lost.
So, what exactly do you mean by saying that you're going to get a "new header two inch inlet two and a half inch outlet". Are you saying you're going to bore out your exhaust ports?
The lack of punctuation in that last bit you wrote in particular makes your message very difficult to understand.
Besides that though, the 1999 Honda Civic Si only has a quarter mile time (stock) of about 15.7 seconds and a 0-60 time of about 7.5 seconds. Meanwhile, the 2002 Toyota Celica GTS has a quarter mile time (stock) of about 15.6 seconds and a 0-60 time of about 7.3 seconds. (
Source.)
None of the mods on those cars are really going to increase the performance of either car much.
Don't ever put it past yourself that perhaps the driver of the Celica is just a better driver than you at this point in time.
I wouldn't waste the time, effort or risk of your life (or anyone else's) to find out which would turn out better in a street race though. Read up, learn about modifications that will actually make your car quicker if that is indeed what you're looking for and then go from there.
If the guy's a douche, he's a douche. You won't change that even if you win.
My god, stop spending money on the car and go back to school.
"Shifting is like unwraping candle"? What‽ How do you unwrap a candle‽ How is it like shifting gears in a manual transmission on a car‽