I have a 406 sbc. It's a stock blocked splayed. Has 12:1 compression with autotec pistons. Rings are gapped .032 and .034 2nd ring. Has 1.5,1.5,3mm ring pack. Leak down of approx. 5% and cranking compression of 205 psi. My question is at idle it'll puff out the valve cover. When I bring the rpms up the blowby goes almost all away. But as soon as the motor decelerates it had a good amount of blowby come out until the motor stabilizes. This is with a breather on each valve cover. Is this normal? I also just pulled my plugs from lots of street driving and they have oil on threads. Btw this is a nitrous motor for those wondering about the ring gap.