Yeah, that is what my inclination is also, the vaccum manual does point to the exhaust system clog. I did the spray test to check for large vaccum leaks, used carb cleaner, the only place where there is any effect on RPM is when I spray it on the air meter plate. The RPM decreases slightly. Could worn out valve stem seals cause such a problem ? I am burning a lot of oil, 1 qt/800 miles. This burning could also have hasten the catalytic converter's clogging.

Thanks George !!

Saumil

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Saumil S. Patel