Some blokes in the know how, (mechanically minded) like above can do it and do it well and safely :-) !

My experience, a couple of so called mates, inserted (ouch :-( ) a $2 joke shop whistle deep up my exhaust years ago for a laugh and forgot about owning up to it when sober.

Took me ages to find/source the issue out and carbon filled my pride and joy :-( !!