UPDATE: to display payment method in order email and alert, copy changes only to the Orders_model.php file if you're running v1.4.2, then use the {order_payment} variable within your mail templates. ex. "Payment method: {order_payment}"
https://github.com/tastyigniter/TastyIgniter/commit/72bde697ef781bd85b5db843cea9f8ae1e14017a