I have a 4" cat delete pipe then from the flange back it's stock piping with a free flowing muffler. I do a quite a but of towing will I see any gains if I put on a full 4" system. I don't want a lot of noise that can't be covered up with the radio. I put the front pipe on this winter and haven't towed with it yet ie I just had the free flowing muffler last year and the egt's were in check. Should I sped the extra $ for the 4" or save it for more mods....TIA