At low loads, these catch cans experience atmospheric pressure. However, when the engine is at high load (WOT), these vents will experience high flow out of the crankcase. This would normally lead to oil and sludge accumulation in the air filter intake pipe. Oil accumulation will occur in the intercooler which lowers the thermal efficiency properties of the heat exchanger and leads to decreased performance.
NOTES:1. The dual CCV catch can kit does NOT address blow-by from the PCV valve side of the crankcase.