why is my 1.5vtec slow in 3rd gear???

I recently did engine swap myself, and the engine has 63k with what
looked to be a new gearbox i have upgraded a few external parts such as

iridium spark plugs and nice set of leads that comform to these plugs,
stainless header not as yet changed cat or back box but will do soon...

my question is the car is very responsive in 1st and 2nd....but 3rd is
lagging and im new to honda but am under the impression 3rd gear is one

of thee best gears, even up after 5and half rev (in the vtec) 3rd gear
is lagging... its as if the vtec isnt working but yet i can hear the
cam opening up. im hoping its minor problem, but have looked at every
angle dont think its a bad clutch maybe iv over looked something, if
someone could help would be much appreciated!!!

oh and could a new external uprated coil improve any preformace??