Loose caps could trigger an idle set failsafe if they were generating interference. They will generate interference if not secure on the plug. A loos cap in and of itself will not smoothly reduce power. Any power interrupts would be exactly that, an interrupt not a reduction.

Ralph,

I'm only telling what I saw. I do not know who the manufacturer was, nor am I questioning your experience with a particular product. If we want to talk specific products I could say that in 6 years and a great many engines and fuel tanks I have yet to see a Viton fuel line leak or fail unless it was chafed through mechanical vibration with a hard and sharp object or melted because of contact with a muffler. From those observations I could make an objective statement that there is no better fuel line, or one that could be expected to last longer. However, that's not my intent here.

I have recently seen two relatively new fuel lines inside a tank split longitudinally. The why of it I do not know. The engines ran badly and after correcting the lines they ran good. The purpose of this thread is to isolate, identify, and correct a problem and hopefully that's what we are all trying to do.