Any egr experts?

[yukon]

I wondering what vacuum the bpt should be getting to work. My vacuum at the throttle is only 1 or 2 inches of vacuum. The egr valve definitely lifts if i supply it with 1 or 2 inches of vacuum. the exhaust line from egr going to bpt doesnt seem to have any positive pressure when i rev engine. I tried to clean it with electrical wire but it still seem to have no positive pressure. any suggestions on how to clean this tube? electrical wire does not seem rigid enough. am i dealing with hard carbon or loose carbon dust? thanks. the electrical wire does travel a long way in.