yes I did open the air scoop you definatly need the extra air flow for cooling,the Hangar-9 planes fly very good not your typical warbird.
I also have a P-40, there solid in the air I haven't seen any of the nitro models clones up close but they seem to look about the same,I have read good and bad about them,mainly the not so great instructs and suspect glue joints something to take a good look at.
another thing is to make sure there is tri-stock in the corners at the firewall area,add some if there isn't, and to fuel proof the fuel tank area with thinned epoxy for strength as well as in case you get a leak in the tank,the fuel can weaken the wood fast and a 91fs isn't a weak engine for sure.