do i need custom tunes after muffler change

[Shorse]

I am really tight on money right now, but after i installed my magnaflow 14" muffler today, it smells like i am running really rich. I'm not sure if it's because i am looking for it now or not, but it is STRONG smelling. I have 275-55-17's, and a little extra weight in my truck tool box( ~200 lbs). Other then that i am stock. I usually run level 2 with the gears and tire sizes adjusted.

If i get a custom tune, i am torn between a 87 fuel saving tune, or a 87 performance tune. My gas millege sucks, 12-14 mpg mostly highway, and if that can be improved with a tune and not effect my perfomance too much, then i'll go with that.

I live in a hilly place out in the country, and rarely go into the city... but i tow my boat every other week (4000 lbs), and a quad on a heavy trailer every once and a while (2000 lbs)... so i need to tow on this same tune also...

what do you guys recommend i do, and can the muffler make a difference at all?