I'm thinking about putting on some exhaust and I see alot 4" systems with 4" downpipes and a lot with 3.5". What is the best for a truck that does no heavy pulling, just runs back and forth to work. Also I was looking at the Summit 4", How are they. Thanks:ro)

You arnt actually changing the downpipe. For you it probably dosnt matter but when in doubt bigger is better. Try to hear a few different systems, sound is very subjective. What one guy thinks sounds great another guy thinks sounds like crap. A flange back or cat back may work for ya too. Or just straight piping your current exhaust.

My 4" Summit exhaust seems like pretty good quality and went on easily. I did it alone in my garage and I'm older than dirt!
But it's loud!

Try to hear a few different systems, sound is very subjective. What one guy thinks sounds great another guy thinks sounds like crap.
But it's loud!
See what I mean, I think my 5" straight piped exhaust is just right with my big program on it.;)