I just got back from the exhaust shop and have my 05 straightpiped but the guy didnt have 3.5 inch pipe and all he had was 4 or 3 so I had him put a 4 inch pipe for the 18 inches or so in place of the muffler. Is this going to cause any problems or is there anything wrong with the pipe going from 3.5 to 4 then back to 3.5? The way I see it the pipe goes from 3.5 through a catalytic converter then back to 3.5 and through a huge muffler then back to 3.5 so it seems like its kind of similar. I don't know. Any thoughts or opinions?

check your private messages.

You should not have any issues with doing this. Most shops that do not have the proper pipe will do this. Other than it looking funny underneath I see no issues. Good luck

What does it sound like? Any "drone" at in town speeds or highway speeds 55-70mph?

I know that mine has some drone but nothing that I can not handle. You get use to it I guess. All the systems out there whether you just straight pipe or install an aftermarket will have some drone. This is from my experience alone. Others will say different. The truck is louder and some say the turbo will spool up faster. To each their own... Good luck

It sounds pretty good actually. You can just hear the exhaust now instead of just the engine.

Should be just fine.

Does the straightpipe mod void warranty?

Generally Dealers dont care if you have a muffler delete. Check with you dealer first if you are worried.