I have a 2002 2500HD Duramax Siverado and I recently purchased a 8.5x20 ft enclosed Trailer with 7" added to the height. My truck knows that it is pulling a load. I am thinking about either adding a chip or upgrading to a 4" exaust. What do you reccoment to give me a boost. I am on a limited budget because I have a 07 Lazer Z XS at my dealer in the crate waiting on me to try to figure out how to get it and not get put out of my house (wife). Thanks in advance for your suggestions.