tone department needs help

[ttfaashred]

I just bought a tube screamer yesterday, and I am very happy with how it's pushed my amp. But i've got 2 problems thus far with my tone. The distortion is almost too buzzsawish, and also I still don't have the sustain for my leads. Thoughts? I traded my cs-3 for it, cause it seemed to really have taken away from my tone. But although I've got a lot of gain now, still when i'm doing hammer on tapping with my sweeps, the notes barely came out, and die fast. My noisegate is set as low without feedback and this is still the case. What am I missing?

Here's my setup

Ibanez S520 w/ EMG 81's into ISP Decimator, into Tube screamer, into Fender tuner, into Framus Cobra, through a Framus Cobra 4x12 straight cab. At the time I don't have a whole ton of money, so if anyone can help me find a fix that'd be great. At the time I don't have a ton of money so a cheaper fix would be good for now, but I need those notes to come out more.