6spd in Civic Si and RSX notorious for 3rd gear popping out and grinding on up and down shift( Honda has a S/B on them for 06-10 Civic) I would almost say Acura does to....I have replaced a half dozen or so 3rd gear sets at work. Easy job, tranny has to be pulled a part but after the first couple there in and out in 5 hours
If you do it upgrade your Clutch disc, pressure plate and release bearing, may as well change out the flywheel to to a lighter one