Corky Bell in "Maximum Boost" agrees with my assessment of the two types of heat exchangers. It is true that the plate type has lower pressure rating, but we're talking about low pressures. 25, or 30, or 35 psi is pretty low pressure for a fluid system, even air to air. Most of the "extruded tube" exchangers have a pretty poor entrance factor, because the tubes protrude past the tube sheet. A shell-and-tube heat exchanger with the tubes FLUSH with the tube sheet will have significantly lower pressure drop, because of a more favorable entrance factor. I remember somebody writing about going into his IC and filling in around the tube ends (maybe with JB weld?) and gaining a pound or so of boost.