I'm working on a 4:54 TAS but i can't find anywhere the 8-1 fpg inputs.

For TAS you can do different input combinations, for example do the 8-1 without slow down, do a small jump from top stair, first possible frame, when you touching flag. Then start to add L presses instead of some R presses like R-R-L-R-L-R-L-R or R-R-L-L-R-R, before you will get first time when you willn't grab the flag. Then normal pole inputs -L-L-L-LA and test some R releases near pole, if it's not work.