Would start looking for any vacuum leaks at all in the system here's a writeup on the older 4.2L not sure if any of it applies to your vehicle but it gives you a start. Other people have talked about blowby from the pistons but I have never experienced it myself, would start with the smaller stuff first. Good luckhttp://home.sprynet.com/~dale02/vac-pcv.htm
87 YJ 4.2L, Weber 32/36, rear bumper tire carrier, nutter bypass, RE 4 inch lift, SYE, AX 15, lined the body tub
"Baby when you said you wanted a project jeep I expected you to spend a lot of money on it" <---Worlds best wife!!!