Cadillac Repair: engine revs, cadillac sls, exhaust leaks

Question
Hi,I have a 1994 Cadillac SLS my engine revs between 700 and 1700 rpm. As instructed I cleared the codes.The current codes are P132 and P042 the history codes are S044,S061,S062,I052 andT072.

Answer
P042 with the 4.6L engine  means that the front oxygen sensor is running lean.

P132 with the 4.6L engine  means that the KNOCK SENSOR has a fault.


QUESTION: Do you have any unusual engine noises or any exhaust leaks, Especially at the exhaust manifolds ?.