It may be that it needs a service, take it would be an 80k service? my guessing would be a main service?
Spark plugs in good condition?
My IS200 has thew joltyness when its on its effective 'choke' stage...it did go when i cleaned the throttle body and run through a fuel system cleaner.
The tapping could just be your fuel injection system.
Do you use higher grade fuel, BP Ultimate or Shell V-Power?
Fuel economy, are your tyres correct psi?
Aaron