First of all, the only Civic 06> that has the "2.0l I-VTEC" engine is the civic sport

and if you have a Vti model its the 1.8L R18

...in terms of maxing out its power...the only way to get anysort of real world breathtaking highly noticeably power gains is through ...either turbo charging..supercharging..or k20 swap (inwhich then..u should of just bought the sport in the first place for that)

nonetheless...if you don't have the sort of $$$ for the t/c..s/c...then there is always intake for starters...and i don't know if there are headers yet made for the R18 ..let alone s/c or t/c..but search is your friend