Hi Bro Zeus,
Regarding the air filter I have some info can share with u according my own experiance. I'm currently using Blitz SUS (Stailess Steel open pod Filter). Advantage is higher reliability that you can service-able to wash & clean many time without wear & tear. Beside that Blitz also design to suit for higher PS performance engine use even Skyline with 1000ps also no problem. By the way suction sound during turbine compress is very clear & loud with solid " Sysssssss" sound:vroam:.
Horse power increase eh...(According Japan Info up 13.9ps
But i not sure) See attachment below.
Finally u worry for open drop filter without heat shield problem that wat i can say is custom made the heat shield only lol... or if u r using Bonet with air-vent is better effect to reduce the hot air suck in coz the hot air easy release from the upper air-vent.
Hope above info can help u to decide which type filter wan to select.:proud: