EGR problem on 92 Tracker: clogged case tube?

92 Tracker, SOHC engine, 4-speed. Troubleshooting an EGR problem (I failed the emissions test), I found that the exhast gas was blocked along the "feed tube" cast within the engine case (goes around the back of the case under the distributor--at least that is where it seems to go). Does anyone have a suggestion for clearing it? Vacuum shows up on the intake port in the EGR valve mount, but no exhaust pressure on the other port.

Thanks, all.