To make the pork: combine first 7 ingredients (-pepper) in a large resealable plastic bag, shake to blend and add pork to the marinade, seal bag and chill overnight, turning bag occasionally.

Step 2

To make the sauce: In a bowl combine first 7 ingredients (-vinegar); season with salt and pepper. Cover and chill until ready to use (can be made one day ahead)

Step 3

Prepare grill to medium heat. Remove pork from bag and grill until thermometer inserted into center of each tenderloin registers 145 degrees F (15-20 minutes). Transfer to work surface and let stand for 10 minutes and then thinly slice into rounds.

Step 4

Grill pitas until warmed through and softened (2 minutes per side). Cut pitas in half and fill pita halves with pork, drizzle with sauce and then tuck in onion and arugula. Serve, passing remaining sauce separately.