both high speed and low speed screws are capped so not to be adjusted.
If the caps you refer to are the 'don't tinker with me' plastic ones, slit their sides and pull them off. You may find that the H & L needles are in fact adjustable to improve the existing carbs operation.
I may look dumb but who or what is RCIGN1?
Particularly liked the WHAT part of your question!
RCIGN is a frequent poster in this and other forums. 'Some have said he has probably forgotten more about engines than you and I will ever know....
' Of course that is just hearsay....BUT I do read alot of his posts to threads to garner helpful tidbits of knowledge. Do a search and it will show his recent posts.