White deposits collect in the pressure taps on the CAI/header box where the prove switch hoses connect. This is preventing the burner from lighting. I pull off the hoses, blow them out, and clear the pressure taps with a wire. Furnace works again for a few days till the build up returns. I've been told that the build up is possibly sulphur, which is a result of the combustion of the propane. What can I do to resolve this problem.

Doubt sulfur from propane. There is a minuscule amount of Mercaptan which is sulfur bearing but not to the extent you indicate. Is this a condensing furnace? Sounds more like mineral deposits from water.

I paid a visit to a Lennox dealer (not the one who did my install), explained my problem. He's the one who told me about the sulfur deposit issue, and that Lennox actually issued a fix. Some Teflon inserts that are supposed to be slippery and not allow the deposits to stick. Spoke to my installer, he had already tried this fix. I have a 3rd Lennox dealer tech coming out to the house tomorrow to check that this furnace was installed correctly, and adjusted properly. Thanks for your reply.