If he's on your 6 diving, usually if you just turn hard once, they will go back up to the stratosphere and wait for someone else who isn't paying attention...
If he stays with you, use what the 190s do best... rolling scissors. Cut your speed and use his against him. I'm no expert on tempests, but get a tiffy slow and tell me how good you get it to maneuver. Thats really all a tempest is: a jacked up tiffy. Also, most of the time, the guys flying tempests hardly ever fly them because they are perked. They only take them out when they are looking for a little variation, so they most likely won't know how to fly um. Just watch out with the scissors, cus he's packing some major cannons, and you are going to have to pass by his gunsights on a snapshot at least once.
But in all honesty, I'd bet a dollar to a doughnut he doesn't follow you if you move out of the way.