The best advice? Look for a different aircraft.
On a normally aspirated engine, with a carburetor, the fuel distribution between all of the cylinders is not equal.
First step: Check the accuracy of your gauges.
Can I have bad rings even when I get good compression numbers?
You should follow the manufacturers recommendations for TBO for your prop.
The best advice is always ask lots of questions, review the logbooks carefully, and be certain to have a good pre-purchase inspection by a well qualified maintenance technician.
The problem in the overhauled Cessna 182 engine is the oil pressure drops gradually after a four to five minute run-up.
"I've spent a lot of money on the project and don't want to risk the new engine being ruined because of eagerness."
The rule of thumb is when leaning, lean to the leanest cylinder.
Paul offers several troubleshooting tips to solve this reader's problem.