2004 Ford Expedition white smoke

I have an xlt that had recently been parked for about a year my truck now has a knocking noise coming from the muffler that gets worse when the truck is heated there is also white smoke coming from the muffler that has a strong smell to it as if something were burning its really shaky while parked and even while driving at some points
it does not accelerate as it should when I press the gas it hesitates to go.
when I turn it on first thing in the morning it hesitates also as if it were going to turn off (sometimes it does) then after a while it accelerates and kicks in as if I was stepping on the gas while parked