One thing to consider is that no matter what product or component you have, you are fighting against the physics of gasoline vapor pressure. What this means is that there is an altitude above which any and all pumps will ALWAYS vaporize the fuel making it impossible to run the heater - probably around 12,000 feet. This is what causes vapor lock. This aspect is due to the properties of gasoline and has nothing to do with Espar or any other heater. Some factors that affect this are: how much "head" is your pump pumping, where "head" is the vertical distance from the bottom of the standpipe to your pump. Other factors include the diameter of the standpipe, the number of 90 degree elbows, etc. In addition, "gasoline" itself is variable, and significant differences in vapor pressure can occur depending on the blend, even with certain standards. As an example, one solution for high altitude carbureted cars is to add 10% diesel, which has a lower vapor pressure than gas. Another solution used by auto makers has been to make the fuel pump a "sump pump", so that the pump itself is in the gas tank reducing the "head" to zero.