A possible clue: From my 1975 Presto Instruction Book Page 41 bottom of page: Hunters Turkey 2-3 Lb Turkey serving pieces. Heat cooker and brown the turkey. Cook 15 minutes with regulator rocking slowly. Let pressure drop of it's own accord. Your roast can't be too far diffrunt.

Agree with both preceding comments. Especially the need for a digital thermometer. Ignore the pop-up, there's really no substitute for a digital thermometer to properly cook meat of any kind. With poultry, it's for food safety, with beef or lamb, it's to be able to cook to whichever degree of doneness is desired. They're useful for far more than meat too. It's the best $10 you'll ever spend. 325 and 350 are really the same temperature, especially given how inaccurate and variable most home ovens are. At the lower temp, it will take a bit longer than 90 minutes, but the process is the same. At the risk of giving an obvious suggestion, remember to allow maybe 72 hours (+/-) of defrost time by moving the breast from the freezer to the refrigerator before you cook it. Also, I always pull turkey and chicken out of the oven at least 5 degrees below the target temperature. When you're clear it's in the high 150s or at 160 in the very center, take it out of the oven so that it doesn't overcook as the temperature will continue to rise for the next 5-10 minutes.

Last time I made one, I seasoned it w/ a rub of ground coriander & Italian herbs, salt & pepper & fresh squeezed lemon juice. I used this recipe from Martha Stewart, but instead of a baking sheet, I used a large round Pyrex baking dish like this, to keep spatters in & collect drippings: Roast Turkey Breast a la Martha Stewart INGREDIENTS 2 tablespoons extra-virgin olive oil 1 1/2 teaspoons coarse salt 1 teaspoon freshly ground white pepper 1 bone-in, skin-on turkey breast half (about 2 1/2 pounds) DIRECTIONS Preheat oven to 400 degrees. Stir together oil, salt, and white pepper brush over turkey. Roast turkey on a rimmed baking sheet until an instant-read thermometer inserted into the center reaches 140 degrees and climbing, about 30 minutes. Let rest for at least 15 minutes. Slice turkey as needed. COOK'S NOTE Turkey can be refrigerated for up to 5 days. NOTE: Mine took more than 30 minutes - more like 45.

It might be a little denser, but not enough to make much difference to the cooking time for bite sized, boneless chunks. Your best bet when making substitutions to known recipes is to use a thermometer. For turkey, (above 165° F), or push the tip of a sharp knife into the center to see if it's past pink, firm rather than glossy, and the juice runs clear rather than dark pink. In other words, yes, you can use turkey. It'll taste like turkey, however, which is a stronger flavor than chicken.