Long time reader, first time writer. This quick & easy mod may not appeal to many of you, but to the some of you want to tone down the engine noise, here is what to do. First go to your local salvage yard (sounds better than junk yard), and pick out some insulation in good shape. I picked up insulation from an Olds Cutlass (GM A-body) and it filled the engine bay completely in the Nissan w/o cutting. Then go to Lowes and pick up some new nylon trim retainers. The insulation was $2, and the retainers were $5. Line up your insulation and push the retainers in the holes. It is that easy. And the results... a much more quiet cabin. I swear it makes the engine sound better because at idle you can't hear it, and at WOT it cancels out the harsh tones and leaves only the purring growl.