What does this kit do? From the factory the S5 4.2L V8 FSI comes equipped with 2 coolant lines that heat up the oil separator at the back of the intake manifold. Why do they do this? This is a precaution for climates that are colder than 32 degrees Fahrenheit. They heat the oil separator up to warm up everything quicker for meeting stricter emissions requirements. This transfers heat from hot coolant to the back of the intake manifold near the throttle body. This is unnecessary in temperatures above 32 degrees Fahrenheit and only slows your car down by heating up the air in the intake manifold. This kind of modification has been done on other cars like B6-B7 S4s, Mustangs, and Subarus for years. JHM has found that this modification works great to keep your car faster once warmed up instead of slowing down when the hot coolant begins running through the oil separator vacuum port.