Put your tenderloin in a large zip lock bag and pour in the pineapple juice, let marinade for 25 minutes. Drain juice when done.
Heat up your grill on Med, when pork is ready cook on barbecue till juicy and tender, approx. 20 minutes, turning a few times.
Meanwhile mix your diced pineapple, pepper, onion and cilantro in a small bowl, squeeze in your lime juice and stir well.
When tenderloin is done slice open with a sharp knife, spoon in your pineapple salsa, cut and serve. The salsa will be enough for 2 tenderloins. 2sp per 3oz or 1pp per ounce of pork.