Tech a says that maually opening an egr valve with a vaccum or scan tool will cause the engine to idle roughly or stall. tech b says that blocking the egr valve passages will have no effect on the obd-ii. who is correct?

This is automotive btw

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)