I am thinking about duel 6in. or 7in. stacks on my 1994. I have three vehicles and this truck is going to be more of a toy than the others. My question is for the people that have stacks on there trucks; are they very very loud, how is the drown on the freeway, and are there any other drawbacks? I have a 5in. turbo back with a muffler on my 2005 and it loud but almost no noise at cruise on the freeway, and I love it. Is anyone running the grand rock stacks with internal mufflers? Thanks for any info.