Green’s Dictionary of Slang

1. (US) confidential, top secret.

1967		E. Shepard Doom Pussy 219: So damn sneaky pete we’re not supposed to talk about it.
2009		A.T. Hartley Sunrise Mystique 163: We were usually all alone, real sneaky pete stuff. We didn't have the support services regular field units had.

2. duplicitous.

1974		G.D. Adams With Loving Tenderness 103: Real Sneaky Pete stuff. Who is the poor bastard you've been putting the arm on this time?
1987		W.T. Vollmann You Bright and Risen Angels (1988) 319: Those sneaky Pete aborigines.