vehicle bogs down at 35 mph and has a muffled sound trying to accelerate.

Hello, I believe you probably have a clogged catalytic converter. Make sure you have about 20 +/-3 PSI while the engine is held at 2000 rpm. If you notice the vacuum dropping, the catalytic converter is probably clogged. In either case, there is a reason for the clog, and oil consumption of incorrect fuel mixture could be it. Best to have it diagnosed, and then follow up to see if there is an underlying cause, or extended use caused the failure. http://repairpal.com/mazda-within-10-miles-of-boise-idaho-83704