HELP spluttering

[partytownsri]

hi i've got a nova sri with a four branch, ported and polished head, powerboost valve and a piper cam 270deg kit, but when i get to about 5000 revs or 100mph it starts to splutter, then i have to slow down and wait for it to stop spluttering so i can carry on. any help would be appreciated thanks.

[Adam]

Check the timing belt hasn't slipped a tooth.

Someone on here a few weeks back had a problem where the engine kept spluttering at higher revs and the belt had slipped a tooth or two.

[partytownsri]

i have check and it is at the corret timing marks

[Adam]

Take that powerboost valve off, it will be messing with the fuel pressure, when the fuel pressure is perfectly fine without it.

[partytownsri]

i have tried doing that but it still carried on splutting, will it need a bigger fuel pump or not