I dunno mines got a twin flap off my evo iv and rattles been offered turbo for 200 so not paying stupid money for half of one lol can you not get the parts to repair the flap?
If you're going to the trouble of changing just the hot side you may as well try to get the 10.5t from the 8MR. Keeping the 9.8t but just having single flap is really only a sideways move and give you no "head room" for future improvments.
Downside of 10.5t when I changed mine was that the spool was a little slower (500ish rpm acording to graphs) but I didn't notice this as I was too busy exploring the top end ;-)