Corrado relay no.72 could be different to a Mk3 relay 72. Saying that because:
http://www.golfgtiforum.co.uk/index.php?topic=74087.0Relay 72 is for the rear wash/wipe function.
Have you had the car scanned for faults? If nothing comes up I'd definately do what harlemex said and get a compression test done.
Few things though, you said intially your fuel consumption halved and the car felt flat... Skipped timing could cause that.
Then the spark sequence wasn't correct, again, cam (dizzy) to crankshaft correlation could be out giving that fault.
Get a compression test done as said or simply just check the timing marks are all in place.
If all is ok, even after changing your relays, check over all the new parts that you have bought. You mentioned a weak orange spark, it should be bright white/blue colour indicating high resistance through a faulty part?
Hope you nail this
