My current set up is Magnaflow true duals (Tru-x di/do muffler) with rear cats deleted. My dad has the same truck with stock exhaust and I tend to think that his runs a little smoother and has a little more pep than mine does at time. Gas mileage is the same, driving conditions are the same. Just curious if going back to a y-pipe and a si/so magnaflow may bring back some low-end power?

Now I have searched the threads and it seems like a typical response is that true duals will produce more low end power but after driving both trucks back-to-back, I feel its the other way around. any thoughts?

 

Stock size single exhaust is the best for low end. Duals you will usually lose low end but gain more high end power (very little gain)
If you wanna keep duals you can run mandrel bent SS 2 1/4". And that should be good for low end.

 

The other way to look at it is this. When driving down the freeway and you hit a hill, where are you in the rpm band? try that comparison. Unless your towing in town stop light to stop light true duals will give you more power where it counts the most. On a hill at 3000 or more RPM's. I've towed 5000 lbs over grades at 6500 ft. and pushing 3500 Rpms with duals and pass other trucks with factory exhaust. The argument can go either way and testimonials till the sun goes down. In the end try both trucks the way you would really use it. Towing a trailer for camping trips into the mountains or just around town will give you your answer for what best works for you.

 

I would regear to a lower size before changing your already aftermarket exhaust.

 

I must agree here. Take the power you have and leverage it

 

This.

Your truck is 11 years old, so any potential sluggishness could be maintenance or engine condition related. Running smoother or rougher doesn't sound like an exhaust issue to me. I have long tubes, no cats, a Y pipe, SIDO, and then another Y for duals. I barely noticed anything with these additions, so I'm a firm believer in exhaust doing absolutely nothing noticeable on these trucks.