Interesting. Top of the page you linked sez (added check marks are mine, to indicate applicable to the Slant-6):
WARNING
This product is not recommended for the use on:
1. Intakes with heat crossovers (√) and EGR values in the intake.
2. Straight 4-6-8 cylinder motors where the exhaust and intake overlap (√).
3. Some castiron intakes (√) have had an issue also
REASON: The polycore is an excellent insulation but it cannot take the extreme heat that the exhaust creates. This causes it to get soft or melt.
