It's hard to tell what you're doing wrong, if you don't say what you're doing. Also, I've never eaten at a P.F. Chang's. That having been said, wok food is all about preparation. The most basic techniques are having a complete mise en place ready; and cooking things separately then assembling your dish in the wok.
If you want crisp chicken, you have to marinate it, remove from the marinade, and toss it in corn-starch to coat. Bring oil to heat in your wok, and chow the chicken in small batches. Fry each batch until crisp, remove, drain, until all the chicken is fried. Reserve the chicken and chow (stir fry) the rest of the of the dish. Make the sauce in the wok with the peanuts, chile, etc., still there. When the sauce boils and the corn-starch brings it together, return the chicken to the wok and toss to mix. Don't let the food sit at all. Get it out of the wok and onto a plate, immediately.
Hope this helps,