Will an ECU program make a big difference in my car? I have i/h/e. I was wondering how much of a performance gain I could expect to see with a Hondata, Mugen, Skunk2 or the likes chip.

 

no chips! they aren't worth it on Hondas. A standalone fuel system (ie Hondata, GReddy e-manage, etc) are great as they can give you better fuel maps with tuning.

If you are going to stick with just those bolt-ons and not upgrade big, you may want to think about a VAFC and FPR instead.