keep the engine cooler but it will raise the boiling point of the coolant that will allow your engine to run hotter without boiling the coolant. The Water Wetter will help the heat transfer and that will help the engine run cooler. However, the engine temp is controlled by the thermostat which opens at a set temp and the amount of thermo valve opening is determined by the demand placed on the engine. Eventually if the outside air is hot enough and/or there is sufficient demand from the engine the thermostat will open fully for max circulation through the radiator. The OEM thermo opens at 170F and is fully open at about 195F.
The extra pressure cap may not be needed if you do not intend to place extended load on the engine like road and track racing for many laps. Plus extra pressure in the system will shorten the life of the hoses, seals and the radiator. You be the judge based on the use of the vehicle. I would try the OEM 1.1 (16psi)cap first which should be more than adaquate if a DD plus some 1/4 mile drag time.
