Hi Mike,
I feel your pain - I have had a horrible season of (not) sprinting and hillclimbing this year as a result of very similar problems.
At one point I replaced the injection relays with the correct new Bosch items (0986AH0602), and one of the new relays was faulty. Whilst it allowed the car to start, the minute it got hot and the ignition was turned off, the car would then not run until everything cooled down. Talking with Techniques' Brian Gateson, he indicated that he has had many duff (new out of the box) Bosch relays, and had experienced very similar problems.
It would be worth pulling a plug lead, popping a spare plug into it, grounding it and seeing whether you are getting a spark when the engine turns over. Assuming that you have a spark at the plug, I'd suggest swapping the injection relays back for your originals, or put new ones in again, and seeing whether that works. I was guided to buy some noid lights (I got Draper ones for £15 from Demon Tweeks); basically, by removing the electrical feed at one of the injectors, and plugging in the light to the connector, you can check whether a signal is getting to the injectors or not. In my case it was clearly not, and replacing the defective relay sorted it out.
There are a lot of supportive people on TalkMorgan with a very detailed knowledge of +8 electrics of our vintage, and I'm sure that some will be along soon to proffer help. I'm definitely NOT one of those knowledgeable people, but I have learned a little going through my troubles. Those more knowledgeable folks may well suggest some simpler/more elegant analysis paths than mine.....
Good luck, and please let us know how you get on.
Dave
