I'm a bit new to the whole car scene so please go easy on me

K so here's my situation..

I bought my Integra LS with 93,xxx miles about 4 months ago with no major bolt-ons just a Greddy SP2 catback and 16" Supermeshs.
About 2 months ago I dumped my car, changed rims to 15" slips, and added a AEM CAI. I have yet aligned my car and fix my camber,
which I will do soon.

So the problem is that I am getting HORRIBLE gas milage after I did these mods. I'm talking about getting like 300+ on full tank prior to
these mods to now just getting 80-90 on half a tank (I never refill my tank full and I have not done the calculations to find out my exact MPG).
I've read articles, forums, etc. about replacing spark plugs, tune-up, and such and I just need to get your thoughts before I go out and spending money.

Also I have noticed it takes a little longer to start up the car, would this have any related effect?

Your help will be greatly appreciated.

 

just do basic stuff, spark plugs, engine flush(seafoam), check your fuel pump.
the modifications you have done shouldnt affect the gas milage that significantly if any.

 

Your estimates are totally inaccurate. For all you know, your mileage isn't any different! You won't know until you do the calculations the RIGHT WAY, which means (a) filling your tank to full, and (b) calculating your MPG between fill-ups. Try that and calculate the numbers, and then we can discuss it. Until then, there isn't any point in even continuing the discussion.