the easiest way to make sure your carb is opening is to just pull on the cable from the top of the carb while holding wot with your other hand. if you can pull the cable up, it means it isnt fully open... done.
that said, it sounds like you're having airleak problems. If you're using the shorty intake manifold, its because the dellorto is hitting the cooling fins and not pushing all the way on, or if you're using the malossi manifold, its because the manifold isn't sealing flat, it has to have a little tabby ground off.
take the motor off, take the whole intake tract apart, clean it all up, cut some new gaskets, and assemble it all together. when you get it running, if it doesn't fix it, try spraying some carb cleaner or starting fluid around the intake manifold. if the bike dies, it has an air leak.
if that seems to be fixed, start looking at the electrical system.
have you read fred's guide yet? maybe try the troubleshooting section of the motobecane manual?