2002 Buick Regal

If it is running lean, that means the engine is getting too much air and not enough fuel. There is a good chance it is caused by a leaking intake. There are ways to test for leaks but they can be dangerous. Some mechanics will start the engine and with it running, spray starting fluid or carb cleaner around the area that may be leaking. If there is a leak, the RPM's will go up. However, (AND KEEP IN MIND) if you hit a place on the engine that is hot enough like an exhaust manifold, it could catch fire. I've seen it happen. Make sure to have a fire extinguisher near by if you want to try it.