They guy is right about the carbs. I've got a Magna as well and they are notorious for getting clogged slow jets if they set up.
You might try running a couple of cans of seafoamâ„¢ through it. A couple of cans will run you $35 to $40 depending on where you get it. There's a passable chance it will solve your problem. It's a lot cheaper than hiring somebody to clean your carbs, and a lot easier than doing it yourself. There's no guarantee of course, but I'd say it's worth a shot.
Seafoam is worth a try. Get it out on the road and blow the cobwebs out of it.