I'm still experiencing issue getting r9 290 to work. I tried everything, using clover configuretor changing fb name fake id clover nothing works. The graphics is really slow it only shows 7mb vram I tried setting smbios mac pro 6.1 no luck 
I have asus z97 deluxe i7 4790k by the way
Just my luck
Give up and install Linux?
Even tho its not legal. You could just buy a premade hackintosh on eBay. It might not have the specs your after. And you wont learn as much.
Or. You could try going to hackintosh threads and ask there.
Not helpful guys. So it appears that getting r9 290 to work in yosemite is impossible
I eventually got r9 290 to work properly for yosemite hackintosh. Someone from hackintosh reddit really assisted me. What a life saver 