Doggepe

Hi, im running FSX on a late 2012 iMac i5 3470S 2.9GHZ. I was at the start really suprised how well it performed in fsx, with all slider maxed out, except traffic & weather it gets about 30-50fps flying a 737 low over manhattan, and about 100-140fps when crusing at 35k ft. On landing/takeoff on for example JFK intl or O'hare i have 60-70fps+. I have recently installed UT2 and some addon scenery such as AS Arlanda, AS Dusseldorf, AS Brussels etc. On those airports without traffic i get 35-45fps+, but with UT2 set to 50% this drops to 20-25 TOPS. Is it normal to get this huge of a drop? Any ideas of what graphic settings i can lower to achieve higher fps than this? I've tried lowering the scenery slider to about 70% max but does not make me more than 2-3 fps difference. *Im runnign FSX steam edition which what i've heard is pretty much tweaked 'out of the box'.