yeah according to Wallace your plug in the pic shows rich so you definitely would not want to go 4 sizes larger on the jets! Get that dist squared away & what apex are you going to grind on? Just WAG ing on the "H". decades ago a company was offering some different holley jets (hi tolerance) or something to that effect & it might be one of them. I dont think holley puts an "H" on their jets but I ain't really a holley guy. Holler how the dist change does