When my old timing light died it was the xenon tube. Really, there was not much more to it beside the little high voltage inverter - nothing so fancy as a delay for measuring advance degrees. The new one came from Sears, and again, I did not spring for the adjustable version; I should have waited for a visit to Harbor Freight because I paid too much.

Anyway to keep this on topic for the OP, I'll post some links to diagnostic and other research I've done inspired by owning 3 k-jet fueled Volvos. At first I thought the misfire might be caused by a vacuum leak -- running too lean, but later, reading the post and noting what had not been replaced, I figure I'd bring my timing light to this problem first. Easily explained by a distributor cap?

Using the K-jet Fuel Pressure Test Kit

0280 800 001 and 0280 800 021 Notes on Operation

Notes on Breakerless Ignition

Also, here are some recent threads from another forum where quite a few still play with these kjet cars.

TurboBricks brand K-jet Fuel Pressure Test Equipment

Building the Best K-jet Fuel Pressure Tester: What Would You Pick?
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Art Benstein near Baltimore

Show me a piano falling down a mine shaft, and I'll show you A-flat minor.