Simcity 4 help, can't get high tech industry or lower pollution?

I am currently building a city and am haveing a problem attracting high tech industry. I have cleared all industrial building witch cause high pollution, leaving only low poluution. I have also put in several parks as well as make the hi-tech industry tax low and even put several program that would attract them, not biotech as i don't have it yet. My pollution is bad and i can't seem to get it to lower also , even demloshing all high pollution industeries still leaves it in the red zone. My power plants are natural gas, so not much pollution there either. Please help and thanks a lot.