from my experience the main reason Ive had for victa only running with the snorkel removed is air flow issues either with a wasps nest in the top part of the snorkel of a blocked air cleaner. try removing the cartridge and seeing if it helps.
as to the seals it is indeed a good idea to replace both but for the top one the top bearing needs to be removed which means dismantling the whole engine. the reason for this is because the old victa engines have a roled flange that the seal sits against so you cant get them out from on top.
regards jay
