i think that 20000/= is okay.bcoz u went to the agents &u changed the petrol filter too.last December i did a tune up for my 121 bcoz of low fuel consumption &low pickup.on that time i changed air filter(VIC).4 spark plugs(toyota),& that wruth chemical,how ever i didn't changed the petrol filter,b coz they said that changing petrol filter will cost about 8500/=& first we will only change the plugs&air-filter,i said OK & they got a DIAG report & then did the tune up.after tuneup,ones again they got a DIAG report & they compared before & after tuneup reports,finally they said that now car is okey & no need to change the petrol filter,now all the problems are solved :-)i cost about 11000/=