I tried injecting a brisket once, didn't add much too it, PIA.
I've put slivers of garlic in butts, didn't go very far in the meat, but around that it was great, but a bit strong.
I've heard of guys injecting butts w/a cajun injector. I've seen them in bass pro and cabela's, cajun butter iirc.
I think it would be worth a try, it's hard to mess up a butt.
I've heard of guys brine'n, too. I think they try it once. Brine pork chops works good.
Do it bryan! Send the results to me.