i found the problem

you're in third gear.
:edit:

not to sound like a dick i wanted to add this little blurb of info

the peak torque in our cars doesnt come in until 6k, when you modified your engine you most likely raised this number. so it won't pull as hard in the low end as it used to. no big deal.

also are you driving more now than you were before? these honda engines don't like getting warm, even with the new k-series we can see the horsepower numbers drop 5% after the air induction side of the engine gets up to operating temperature