[T3] missing on cylinders #2 & #3 FI 72 Fastback

[Vern Creamer]

Newbie lurker joining the fray.  I have already learned a lot from this group.

Had the engine out last week for clutch repair; installed new spark plugs while the engine was out.  Ran terrifically for the first 100 miles or so, smoother than ever.  Over the last 50 miles, it's been missing as I rev up each gear; sometimes, it gets somewhat smoother once I get over 50 or so.

So far, I've replaced the (brand new) spark plugs ... #1 & #4 looked perfect; #2 & #3 are fouled black ... all of this after just 150 miles.  When running, all 4 plug wires spark when loose but held close to the distributor.  When I back #1 & #4 away, the engine begins to stall; when I back #2 & #3 away, there is no change to the engine.

The next thing I'll check are the plug wires; after that, not sure which direction to go.  Suggestions?

Vern Creamer
Omaha, NE