Those of you with the stock Q-jet may have exp'd this problem. When you stomp the pedal WOT at low speeds the car falls on it's face then kicks in really strong. Commonly this is due to too much/too little AV tension which can easily adjusted by following the tech article about it. One extra tip I would add is to leave your air cleaner off when you test drive it after you make adjustments, You'll be able to hear the secendaries open and decide how much tension to add or subtract.

The other host to this problem is the valve sticking. The shaft bushings wear over time. Mine are so worn that the valve plate shifts back and jams up against the air horn. I'm cheap, I was not going to shell out the cash to get rebushed. My solution instead was much more simple and FREE!!
All you need is a paper clip!!!
You don't even have to remove the A Cleaner.
Just pop the lid, Loosen ONE of the 2 Torx bolts in the airhorn by the sec.'s
Now wrap the paperclip around the bolt and bend it down into the secondary's valve. Pull out your little snips and cut it so the valve hits the tip of the clip just before seating fully. Done. Worked wonders for me. Brought the smoke back to my tires!!! No Shift!!!