So I need a compressor that puts out less air? Or a higher flowing exhaust? Or do I need to simply burn more fuel?
Well to try and explain this easily, your situation will not be solved by doing any of the questions that you have asked above.
All turbos have a surge limit or characteristic and if anyone tells you otherwise then they are wrong. Maintain pretty much described what surge is. It's when you are putting out more Air flow from the compressor side of the turbo into the engine that can't be use. This creates a stoppage of airflow and causes the compressor wheel to "stall" or slow down, but the compressor wheel doesn't want to slow down because exhaust gases are still driving the turbine and ultimately the compressor. This stalling creates added stress to the shaft connecting the compressor and turbine wheels and can result in shaft failure. The main factor that causes surge in our case is engine load, i.e. towing heavy trailers (in your case), or wide open throttle in some cases.
Unfortunately our stock turbos will operate in there surge range, especially when are running hot tunes. Hot tunes equal more fuel, which equals more flow through the turbine side, which equals more flow (than normal designed for) on the compressor side for a given load.
The solution to this is to do something to the turbo so it will never operated in it's surge zone for all throttle positions and engine loads. Or replace the turbo with one that will never operate in its surge zone on our engine.
Here are some of the options that have worked we'll in the past for people.
1) Replace the compressor wheel with a Wicked Wheel, this has not always completely eliminated surge in all cases. ($60)
2) Replace the compressor housing, which will change the flow characteristics of the compressor, an ATS compressor housing will do this and has been known to completely eliminate surge very well. The compressor does not change the air flow to the point you will see better or worse performance it just puts the turbo out of its surge range like we want. ($400)
3) Replace the turbo will one that will not operate in it's surge range, i.e. the turbonetic BB drop in, Garrett 38r BB drop in are the most common and will not surge, of course this is a much more pricey option, but you will notice a good increase in pulling power and performance.
Well that's enough of me rambling, hope I haven't confused you and this helped a little.