The SB says inspect EX-00021 Cylinder #1 exhaust tube and EX00022-1 Cylinder #2 exhaust tube for cracks as described in this document. If cracks are found in either tube, replace the EX-00021 with the EX-00021-1 AND replace the EX00022-1 with the EX-00022-2. Our Cylinders were inspected and have no cracks. Re-inspect every 25 flight hours.