sounds like you have a head with larger exhaust and inlet valves maybe.
what size are the inlet valves? Is it ported and polished too?
You could try contacting tho's company's who make big valve heads. ?
but then again, you are talking about a 10v turbo head. so i don't know if the valve sizes are suppose to be the same as a kv or not.
someone else on here should know better than me, but all i know is that the valves in my engine have been increased from 38mm to 41 on the inlet, and 33mm to 35mm on the exhaust!
Big valve head tuners were ppl like: TSR, GTI ENGINEERING, etc etc. there are others.
hope this helps.
