ever done GST tag purification?

I am purifying a GST tagged protein with contaminants!. How do I get rid of them. I need active protein, what conditions I can change. The protein is found in inclusion bodies and I extract it with sarkosyl and Triton X 100. I have tried 500mM salt conc. in wash buffer, extensive washing, addition of glycerol and low resin bed volume to allow competition for binding. What more I can do to get rid of the non specific bands.

Yes I see the contaminating bands in the elute when i visualise it by SDS-PAGE. But they dont seem to be the degraded products as I can see the contaminating bands of higher molecular weight, when compared to the expexted size of protein, also. I assume that these are the host protein copurifying with the recombinant protein. I need to find a way to minimize the possible non specific hydorphobic interactions. I read in amersham handbook that reducing sonication time helps but I wonder how.