Marty...
As new as your system is, I'd be willing to bet that the Unitrol is in good shape. Since you've replaced the regulator, there's one thing left to do. (And by the way... it's periodic maintenance, as far as I'm concerned...) That's to clean the jets. Compressed air alone won't do it. You have to "drill" them out. It's important to NOT make them any larger when you drill them.
Go to a welding supply company and get a set of "tip cleaners". Basically, it's a set of tiny drill bits. there are a couple of different kinds. One looks a lot like a folding allen wrench set. (Don't get that one, unless it's all you have available.) The other looks a lot like an exacto knife... It's a tube, about 4 inches long, and the bits are stored inside of it. (That's the one you want.)
On the first jet you clean, start with the smallest bit and work your way up, until you feel like it's biting into metal. Than go one size smaller. You don't want to remove any metal... making the jet orifice any larger. Once you've got the right bit, clean all of the jets with it, then blow them out with compressed air again, before reinstalling the burner.
Obstruction of the jets is as much a residue problem as anything. Typically, it happens over a period of time of a year to two years. In my experience, it seems to be due to the perfume added to the L.P. And sometimes, they seem to add too much. That perfume leaves a residue. And if there's too much in a batch of L.P., it will clog the jets quicker.
