HI,
Fuel Pump guys are the right ones. But at idle speed, the engine is reviving in low and high accelerations means, then i dont think this is a problem in PUMP.
Because while servicing they will check for the high pressure in the pump room.
But if you feel the pump is an issues, then the PUMP guys are the right person.Ask whether they have any pump available.. If yes, test with that and check.
Before going there ask your mechanic to check the clutch. The one who fiited the clutch plates. Normally there will be 3 kind of clutch plates are there in market.Compare the old one with new one.
Springs will be differ in the clutch plates.
1.Injector tubes check.
2.Clutch adjustment check.
3.Crown will not give problem like this, but may be.
4.Check the brake cylinders also..This might be like comedy..But kindly check whether the drum is heating.