hi everyone! i have a 1990 audi 90 quattro 20v (7A Engine) i am after a way to get more power out of it. so far i have an uprated K&N pannel filter straight through decat stainless exhaust and have had the head skimmed. is there any other things i can do to my engine to squeeze as much power out of it as i can without going turbo?

thank you all.