Before I start doing anything I would like to try to get an idea of what the problem might be with my tractor. I started it recently and the motor was making a loud poof-poof sound that came out the exhaust and the intake breather. I saw that the clamp on the turbo was loose and I put my hand on the turbo and I felt a hard hitting on the intake side. I tightened the clamp and started it again and the noise had become softer but still the poof-poof out the exhaust was noticeable but hitting on the turbo had disappeared. I tried one of those doctor type stethoscopes to see if I could pinpoint anything but could not find any difference in sound from any of the pistons, valves or turbo. Someone suggested a faulty injector or bad valve. Anyone have an idea what might be wrong or how to check out the problem?