Hi all, ive a problem with my vauxhall vivaro 2005 model,i put some egr cleaner in my tank ,and since doing this ive occured a tapping noise since adding the cleaner ,local mechanic thinks the cleaning additive as worked but probaly got a bit of carbon stuck on a valve or a lifter ,he says told me to drain oil and do a engine flush and get some good oil and filter ,is he right in saying this ???????????