I have a 99 civic si with a b16a engine that has some mods. I'm thinking of buying an apexi s-vafc but i dont know if this will work.

I can use a little help please

Engine Specs: cam gears, cai, header & exhaust, port polish, fuel press regulator.

 

if your going to buy an afc, then take ur cvar to the dyno so they can maximize the power output. but honestlky, there not worth the money unless u have some heavy head work and some internals done. first, go and tune it, tinkering with the cam, ignition timing and also mess with ur FPR. if ythe tuner sasy u can benefit from getting deeper into tuning, then go for it. other wise its just bling.
if u plan on sticking NA, put that money towards ITBs, then u could make use of that afc/ good luck