hell, the japanese regularly take the drift s13's to 8500 with just valvetrain and ras.

but alot of them use the s14/s15 sr's which have stronger oilpumps.

then there'st he drag sr crazy people with 10k -11k motors

and the non turbo guys and the primeras of the mid to late 90s competing in the btcc turned around 9-10 also.

keep in mind as the rpm increases the cost to keep it together increases exponentially.