Vauxhall Vectra engine lose, mis firing or do i scrap car

hi all. I really do hope that some one out there in the car world can help. Got my vectra, it run great. was a lovely car. It had to have its mot done. So, took it in. It failed on some minor things. taking it home to sort them out, the car started to misfire, then go ok. It now does not run. called mot centre to see if they had done any thing, nope they had not. finally got through mot, but it would still mis fire. Not great on motor way. took it to many different garages. Had so much done. New spark leads, coil pack, head gasket fitted. new clutch. Had the car hooked up to have readings, reader found nothing. When tryed with a mates reader, it kept saying it was not conected to car. He then tried another car and it worked fine, just not on mine. Well, the vectra has now sat on my drive. Ive spent hundreds on it. Another place said i need a new ecu. Great if i can find the old one. Dont want to get shoot of the car, but it is looking more and more like i have to. Even vauxhall garage cant work problem out. I hear that its a common problem with 1998 vectras?? but no answer on fixing. PLEASE, some one, help