yup... the kir kir sound on idle must be the tappets asking for an adjustment 
the kir kir sound while driving would be knocking, if u are driving on petrol.
as for engine getting noisy at above 100kmph, there can be many reasons.if u think its the exhaust, park the car over a pit or simple jack it up from one side, ask someone to sit inside and rev the engine while u try to hear if the exhaust is leaking from anywhere.
btw, at just 30,000kms there it is very hard to believe that there wud be a problem with the exhaust.try to explain what kind of sound it is, it can be sound of a wheel bearing or tyres themselves, may be timing belt bearing too.
