Hi I am new to mac, i am running Autocad on a 27" iMac i7 with 12GB. I am having some problems with the graphics, sometimes quets slow and sluggish. Is there any way to enhance my video card? change it? boost? enhance? clean? Anything?????? The video card is: ATI Radeon HD 5750 1024 MB. Will any setting on the computer help the performance??? Thanks for your help!!!