RE: Do the 2.5 and 2.5R have the same Carb?
Yes, the 2.5 and the 2.5r use the same carb.
From the photo it does not look like you have o-rings on the OS carb. That could be why it's loose. You don't want to use it if it's too loose. You want a snug, sealed fit or you will have air leak issues.