big valves giveing 30 BHP LOL
valves in the 8v head are plenty big enough, if you just duff bigger valves in a standard / standard ish head it'll usally make less power.
i would ask them to provide before and after flowbech readings for other heads of the same spec they have done, and if you have your head done flowbench readings for it before and after.
i would go with new guides cut back and taperd, reshape and polish the valve back then have the valves and seats TRi cut with 30 degree seating face about 60 tho / 1.5 mm thick, deshrouded the valves as much as possible and match the ports to manifolds and a 16v downpipe. that should make it a bit fitter
