Consider that foam may trap moisture, either from water intrusion or condensing.
If you use sound deadening pads you will get significant improvement, removing the tank to install if necessary, in the pillars will offer less result as those areas are small and tight which resonate less. Larger the span the more it resonates.
Summit has their own brand peel and stick rubber/alum pad kit that priced out well. Still have extra laying around.
When I did inside the door panels, floors, firewall, and cab rear lower half I got significant results, if I had done behind/above the headliner I would expect added reduction (is added reduction and oxymoron? How about further reduction)
The doors sound more solid than I expected when they close instead of tinny, even though I did not do the outer skin (so they could breathe).
Chuck
