Hello!
injector level is not the problem......its for getting gas inside carb........
there are several causes that on max RPM engine gonna miss out....
check Airfuel mixtures as much rich mixture or too lean makes engine lag on high rpms.......this can be adjusted through Idler screw and then the T-bolt located on main gas line going from Regulator to injector.......
make sure ur air cleaner was not clogged.....and air intake was not so much blocked as on high rpms it lags when air intake is restricted much as needed
do check for Plug wires and Ignition coil.......make sure none of plug wires is weak or broken and ignition coil is much enough good to gave a strong spark......reduce plug gap to 0.6mm as defualt was 0.8mm......
check timing..make sure its advanced...not retired.....as CNG need timing advanced around 15-16degrees BTDC.
no reason that its gonna lag on high rpms after checking that stuff.....there must be some things which i mentioned mess up..
Thanxx