Car-99 civic dx hatch

Motor-98 usdm type r engine and tranny

Only cel code is for secondary o2 which is not wired in

Mods-dc sport cat back and header

Problem- vtec seems to not "pop" until about 6800-7000 rpm

Background info- recently bought car from a very good freind he has had the car sittin for about 2 years starting it and what not every so often during that time (reason for sellin he bought an sti) car runs fine no hesitation no burning oil nothing escept the late vtec engagement the car is currently running a type r ecu...was driving one nite and it started to feel like a fuel cut when reaching 6800-7000 rpm where vtec was approaching so I unplugged tps and plugged it back in and was fine tho the tps is giving correct readings...just wondering where I should start to diagnose the "problem"

Things that will be done tommorrow
Fuel filter
Oil change and filter
Has new plugs

 

Chipped ECU with a late crossover?

EDIT: Nvm you're running a stock ECU.

 

Low oil pressure?
Faulty vtec solenoid?

 

Its not a chipped ecu its definitley stock and if it helps car is obd2b and I dnt believe I have low oil pressure...any other ideas?