I have an 87 YJ I recently purchased. It has a 258ci in it and a NON OEM carb. Before I tell you which carb (to keep info from being skewed by opinion) I will discribe the problem. I have the OEM Motorcraft ignition system installed.
First question, Does the feedback carb system affect or ajust the ign at any point? I have worked on several types of feedback systems and none affected the ign.

When idling the engine will randomly miss and sometimes stall as a result. The missing also will at times miss at hwy speeds. On my way back from a ride while cruising on flat road, even throttle, dry conditions, it will have a hard random miss. Once, at the above conditions, it cut out while in 4th gear (BA5 4spd) for about 2 seconds, then restarted (still in gear), it bogged heavily as if there was a complete loss of ign.
I have replaced while this condition has continued, plugs, wires, cap, rotor and a new OEM coil. No I was not throwing parts at the problem as all these components needed replacement badly.
I am also getting really bad valve ping when easing into the throttle say while cruising in traffic, 3rd gear 2K rpms or 4th gear below 2500rpms. My timing is set at 6*BTDC, but the ping will occur as low as 3*BTDC. I am not a fan of the Motorcraft ign modules as they like to leak off their dielectric and cause sypmtoms similar to mine.

My vaccume advance is working, but I hate the fact that the OEM distributor leaves the vaccume advance arm open to debris and water.
Second question, has anyone upgraded the distributor to something a little more waterproof?
BTW I did a search and spent some time researching, and I learned that if anyone brings up GM HEI....don't say I didn't warn you. <img src="/forums/images/graemlins/pfft.gif" alt="" />
Basically, I am thinking about replacing the ign module, I know some of the parts chain stores have testers for them but the kids that work there usually are not bright enough to hook them up much less read the results.
Oh yea, 500CFM Edelbrock performer on an Offenhauser intake.
<img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" /> <img src="/forums/images/graemlins/pfft.gif" alt="" />