Flat spot around 80mph when giving full twist of throttle

[99valk]

I have a 99 std with K&N (using the foam) drilled out first set of baffles in stock exhaust, stock jets, dyno jet stage 1 needles.  The only recent change is the dyno jet needles.
when going on the highway around 80-85 and you give a quick full twist of the throttle the engine boggs down for 1 or 2 seconds then comes back to life, but not at the normal throw you back.
I think it is starved for fuel but I wanted to make sure before doing any major work.
I checked the vent line and petcock lines to the tank and they are ok.  I took the petcock apart and cleaned it.  I tried to test where you apply vacuum to the petcock and it did not leak.  Looking down the fuel tube I can not see the diaphragm move when I apply vacuum.
The bike runs normal and has full power at lower speeds.
Any idea or suggestions, I head to Sturgis in two days.  I can live with the bike the way it is and I don't want to do much messing around right before the trip.
If it ever stops raining long enough I was going to put the stock needles back in and see if the dyno jet needles are the issue.

[roboto65]

Most likely it is the needles I myself might raise them one notch or shim the needle up to richen the circut also maybe open your pilots 1/4 turn .. I suspect you are lean  and when you ask more of it it just cuts out from what I have seen of the Dynojets needles they have alot thinner needle profile compared to stock what do your plugs look like?

[aslondon]

Please correct me if I am wrong.  If the needle profile is thinner, won't that already richen the mixture?

[sandy]

Dyna-Jet suggests that the needles be set on the 3rd notch down from top. This is a slightly rich mixture for more HP. I set mine on the 2nd notch and opened the pilot screws to 2 1/2 turns out. The roll-on hesitation is minimal and I get 36-40 mpg on the highway.