i've built up my engine and now finally got it on the road its a 1.6 cvh, with twin 40's on it xr2i cam, ported polished head, four branch and a vernier pulley. runs and drives fine untill it hits 5000-5500 rpm then it missis and sluters like theres not enough fuel getting to the carbs. i turns the regulator up abit and it made it worse. some times this does not happen and it pulls strrong all the way up to 6k.

any ideas? please help