Sudden RPM Loss?

[Skools Out]

sounds like 1 of 4 things i seen cause this

1: Replace all the plugs may be one bad plug

2: Check for fire on all cylinders could be bad coil pack

3: Check that Magnets are still in place under the flywheel should be able to without removing it

4: Test Compression let us know all ya find

Good Luck Hope it's not an MJ type motor issue ???