I have an 87 westie with spark misses at the coil wire.  I connected my
timing light to the coil wire and noticed a spark miss at idle.  As I rev
the engine, the spark miss becomes even more prevelant and the gap in strobe
light increases.  I have replaced the coil and the distributor (for other
reasons) and cleaned all the grounds.  The coil wire is new and resistance
is good.  I went through the tests according to Bentley and Pro Training
manual and voltages and resistances checks out.  Alternator is good, battery
is good.
Is it time to remove the wire loom covering and start tracing wires or am I
missing something?

This problem began after a shop replaced my engine several years back.  They
even swapped ECU's to no avail.  They did not methodically troubleshoot.

Are there any other components that will drive spark that I need to look at?