ah, there is the thing, u cant test the resistane of teh ect circuit with teh ecu inplace as you will see the input impedance of the ecu itself in the circuit aswell, thats why u must have the ecu disconnected to measure out the resistance, if u unplug the ect and measure across the ecu multiplug, you should see open circuit (ie infinate resistance) now short out the two pins in the ect plug and measure at the ecu plug again, the resistance should have dropped to less than 1 ohm, while u r measuring this, performa 'waggle test'. ie grab all the loom and waggit all about, move the wires around the location where they sit normally and see if the short circuit opens . the probelm with old car looms is that the copper work hardens with age and heat, when u unplug it and move it it may make contact again, but when its all back in its original location the break in teh wire may now be apparent.

dont forget electrical problems on cars are not usually complicated, just hard to locate, and 99.9% of car electrical probs are down to bad or corroded connections. which leads nicely onto the next bit...

have u had teh 2 multiplugs removed yet from behind the headlight near the ignitiopn coil (they join the engine loom to the car loom) and these notorios for fcukin up , they could not reallyt be in a worse place, right under neather the bonnet vent, rain= drips in = water in connections and over the years teh connections rot away and cause all sorts of wierd things. many people (me includd) have chopped these wires out one at a time and soldered them together so that a good eledtrical connection ismade. doing this does afect how u work on teh car as there are literally only a couple of retaining bolts thathold the whole loom to the engine anyway and the whole thing ca be moved out of teh way if u need to work on the head etc..

have faith... u will find it and it will be something simple