I use a marshall mode four. I play loud and heavy, but I also like the clean tone. right now my clean tone is noisy , weak, and my heay is full of unwanted hiss and I cant get a nice change between the two. (clean to heavy) what type of gate could fix this

You can get the Boss NS-2 Noise Suppressor Pedal. This is the pedal I use to cut the hiss. Like any noise suppressor it only cuts the hiss when your not playing. You can also look into a noise filter..

http://www.theguitarfiles.com/product_info-43-400.html