Astra 160IE - 1998 Model Not Starting

South African

I really hope anyone can help, here goes:

The battery on my Opel Astra 160IE was flat, I needed to jump start the car. For some weird reason the + wire was blackish and the - wire was reddish! So in the morning rush, yes we were late, and gedding the kids in the car etc etc, I accidentally connected the jumper cables incorrectly. Sparks flew all over the place and I ripped the jumpers of.

I then corrected the jumper connection and the car started but did not want to idle. We 'fixed' this by tuning the idling screw below the petrol cable thingy so the car would idle really high, this was a temp fix. I drove to work like with this 'fix'

After work I then replaced the two 12v, 30A relays that's situated under the bonnet, the two purple one's. That sorted the idling issue. So I re-tuned the little screw and the car idled nicely at 1000rpm.

I drove like that for about a week with no issues, apart from jumping the battery every other morning. One morning it would start, the next I had to jump it. So I decided to buy a new battery because I still had the dodgy one. I bought a new Willard battery. The technicians removed my old battery, they replaced the one battery terminal, that's the one with the earth wire attached, then they installed the new battery, fastened the clips and voila.....

The Car started great, but it idled at about 500 rpm and wanted to cut out, no amount of stepping on the gas made any difference! The battery tech's tested here and pulled there but still the car didn't want to pick up any refs. When I floor it the refs would go to about 1500rpm very slowly, but there was absolute no power! When I release the gas it will stutter but not cut out.

Another specialist came to where me and my 3 years old daugther were stranded, in a rain storm, he checked the fuel pipe etc, he could not get any fault and eventually gave up.

I had to push the car home, in the rain. Lost my cellphone in the process! The car idled the whole time, at about 700rpm. It had no power though..

I tried to start it again at home, it did start but still absolute no ref's or power. I checked all the little 10, 20 and 30 fuses, none were blown. I then took all the relays above the fuse box underneath the steering wheel and replaced them, all but one. This is the part number: 90159406, I cannot get this relay from any dealer and have to order it online. I am also unable to find out what the function is of this specific relay. Does anyone perhaps know?

After replacing the relays that I could,except the one mentioned, the fuel gage and my windows functioned again. But still the main issue persist. I had one dude run some diagnostics and he thinks the ecu is stuffed..... I just cannot understand how the car drove for over two weeks after the jump start issue, and just after replacing the battery the ecu went bust!? IS THAT POSSIBLE?

To replace the ecu is very expensive, especially in South Africa! Does anyone have any other advice other that replacing the ecu? Could the problem be that one elusive relay? Any feedback will be hugely appreciated because this is my only means of transport and the money to spend is really tight!