There's a ticking coming from my engine which speeds up or slows down as the revs do.
When driving it today I also had a brief 'flatspot' in accelaration as if some of the horses were missing. The exhaust sound was dull for a bit too and it's normally a little 'raspy'. This was in 5th gear at about 80mph and came down to 60mph. Came to a roundabout and give it some whelly and it hesitated for about 2 seconds then was fine and has been since. Done about 40 more miles with no issues but then noticed this ticking when I pulled up at my house.
No engine lights. Engine temp ok (although new thermostat needed). Oil clear but haven't had time to check the level before it got dark.
Could also be a hydralic lifter. My TS 'taps' with the revs occasionally. It might tap one day but not the next. You can dry putting a bottle of additive in to clean lifters. I put a bottle in, drove it lightly for about 500k's, changed oil. About 8 months later its just started to tap occasionally again.