[j cAT]

exhaust leaks do cause the O2 sensors to report a lean condition so you will burn more fuel this can cause the converters to run too hot. using a vacuum gauge see if there is a problem with the engine/restricted exhaust. if the engine is restricted on the exhaust then the vacuum will drop with higher RPM this is because the engine is a pump if the output is restricted the the input cannot suck . follow instructions on how to use a vacuum gauge to troubleshoot engine problems .. since this is OBD1 need to use the old testing stuff for finding problems.