Q: 1999 Toyota camry le gets really loud when accelerating but muffler new

Hello. You are correct. The most likely cause is going to be a faulty gasket. Look at any joining sections of pipe from the exhaust manifold back. It is often hard to check certain parts, and that is where exhaust "sniffers" come into play. These are devices that detect exhaust fumes and can pinpoint a high concentration of them coming from a leak. There are other versions of these tests as well. You can also verify the work that was most recently done was done correctly. For more help, contact our service department to schedule an appointment.