Bad timing, I need to do wheelbearings and hubs on my 96 X90, and my wife's 97 suddenly developed a huge miss just before I got on the freeway going home friday. Code scanner says EGR, I cleaned it with carb cleaner and it functions with me sucking on a hose to diaghram. Could it be a bad EGR modulator?
Checked plugs and #2 looked a little dirtier than the rest. All looked quite used but none really looked fouled.
Checked cap/rotor, rotor looked nasty, scuffed it up with fine (400) sandpaper and put a new cap on. New rotor as well as the rotor from my 96 won't fit on the 97 distributor, the 6 flat drive on the 87 seems to be just a little bigger than what's available (Autozone lists the same part# for both years, and I would expect that).
I gotta have both cars running by sunday night. PLEASE HELP!!!
I'm worried that cam belt might have jumped a tooth or something.

Two thing so check I have had happen with 16V motors.... 1- Check the plug wires... I've had them get old and worn and start arcing to the valve cover causing this... 2- check the crank shaft pulley key way.... they sometimes wear out....

Zig

Timing belt jumped a tooth?  Not likely.  I don't think this happens near as often as people seem to think.
Bad EGR modulator?  Not likely.  Pretty simple and basic device.
What it could be is a restricted/clogged EGR passage.  The EGR passages are known for getting restricted/clogged.  There is an external metal tube on the passengers side of the engine, a passage internal to the back of the head that runs from the exhaust manifold over to the EGR valve, and a passage from the EGR valve to the intake area that all usually cause problems.  You can clean them with aerosol brake cleaner and a stiff wire or old speedo cable, and compressed air.  It usually takes a lot of spraying, jabbing/poking and air to get the passages throughly clean.  Also, the EGR valve itself can get build up in it and need cleaned.   
One way to isolate which cylinder is missing is to pull the spark plugs wires, one at a time, then reconnect.  When the engine runs the same with a particular wire disconnected, then you have found the cylinder with the issue.  It could be a spark plug, a wire, the distributor or the piston/rings/cylinder itself.  Usually, it is a faulty plug or wire.

Ended up being a cracked plug wire boot, #2, way down by the plug. Didn't notice it when I pulled plugs at first.
Threw #2 wire from mine on it and it's all good. Got a new set and it's running fine.

I was just frazzled as I had to do wheel bearings on my '96 X90. Gotta make a spanner tool. Not a problem, I have a mill and lathe in my garage. Just need to pick up the pins at Production Tool. I just cut the damaged side nut as it was mangled.
I'm waiting for a new retainer nut, so wife's '97 is getting double duty, running about 140 miles a day (we work different shifts).

One thing that baffles me is the distributor rotor is different from the typical '96-'98. It doesn't fit!
The 6 sided drive is a slightly different shape. The 3 smaller alternating flats are smaller, making the wide flats in between, even wider. I don't know what model it came from, but the correct part# doesn't.
Can the drive button on the distributor shaft be replaced? Is the correct end available? Or even easier, what model could it be from?

Glad you got the miss fixed.
Got a pic of the distributor and rotor?  Hard to tell what you have by a description (for me, anyways).

Can't get a pic until tomorrow, wife has it at work, I work days.
The simplest description is the drive on the typical X-90 or track/kicks looks like a hex, the one on her car is more of a triangle with the points flattened a bit. Still a hex, but exaggerated in a triangular direction.

The majority of the disty shafts I have seen on 16V trackicks have been the triangle shaped ones.  I don't recall seeing the hex type.  I know anything 95 and older had the triangle shaped type.  Maybe they changed the distributor shaft when they went to the coil/distributor combo in 96.

Both are triangular with the points lopped off. One is just more pronounced, and one is closer to a hex.
The one every parts store I've been to is the same, closer to a hex.
Her car has the more pronounced triangle style.

What a PIA...lol... I just want to change it to keep the maintainance schedule together. The old one is working fine. Just cleaned up the coil contact with 400g sandpaper and cleaned it with carb cleaner and compressed air.