03 Duramax oil leak

My son has a 03 Duramax that the other day blew oil out some were. He had it plugged in and it started fine. Last week he put a after market high idle kit on it. It brings the idle up to 1250 or 1700 rpm. He said the oil is coming from the right side of the motor. Last night he couldn’t find any leaks when this happened he lost a lot of oil(very low on dipstick) and left most of it on my driveway while it wormed up. I don’t know much about diesel motors but that a lot of oil to come from the breather. I think It has to do with that high idle kit setting to soon after start up. The motor runs very good and has 200000 miles on it. Any ideas would be greatly appreciated.

With the very cold Temps the oil is super thick. I think what happened is the oil was too thick to circulate and got by the oil filter seal. Your high idle might have caused it to have very high oil pressure at start up.
If you have ever noticed at cold start up your oil pressure is higher than at normal operating temperature, especially at idle. I’ve seen this on gas motors also.
Just my guess.

We were hoping it was oil filter but that side of the engine is clean. the filter is on the left side and the oily side is the right side.

That much oil will be easy to see where it us coming from. Find the leak and diagnose from there. Random guesses from the internet are not going to help much. Also why after 200k would you feel it needs a high idle kit added, was there an issue?

You would think a oil leak like that should be easy to find but last night there was not a leak to be found. So for the high idle kit, he is a 19year old kid and bought it over the summer he thought the new ones have them he thought he would put one on his.