52.5 pilot gave me shot gun blast back firing on decel.
55 back in and it floods it out.
By the way, I have tried to adjust the pilot screw to no avail.
I have replaced my old pilot screw because of being stripped.
Just wanted to go thru the symptoms it might point you in the right way.
1st, shot gun blast, it does it on decel, also shut down?
When my header leaked (loose bolts) I got the blast on decel and sometimes shifting, and shutdown (if I remember correctly, it's been a while) Tightening the header bolts resulted in the normal poof on shut down.

2nd, floods out, only at idle?
3rd, you have replaced the pilot screw, was it the right one? Sounds like there are 2 different types from what another has said. Did the ends look alike? same length? etc.
I would say check the header gasket and the muffler connection for leak (candle flame sounds like a good way to check)
You can drill out the 52 to match the 55 or some where inbetween. Personally, I wouldn't do this, but only as a last resort just before you get the shotgun.

I think either you got the wrong 55 or the pilot screw is the wrong one. But check the header 1st.