Who is running a Quikfuel 450 on their Slant

That "might" be some of the issue. I have my stone stock 170 up around 12. Is yours completely stock? If not, it probably needs more. Mine loves the additional timing. I have it on the edge though, ONE more degree and it starts a little bit of a rough idle. lol
I will give that a try when I get the secondaries adjusted, right now they are opening too early and bogging when I floor it, so yesterday I turned it back to the position it was in from the factory. I turned the secondary screw one turn out before paying attention to the floats. Right now, if I do not kick in the secondaries I do not get any hesitation, but when I kick them in I get a bogging sound. I will test it out this morning and may need to adjust it more.