I am not sure why you want a higher peak flow reading?
Sift through those links and educate yourself about what asthma is and how it's best managed. Then you can discuss it with your doctor as chances are, you'll know yourself better than s/he will. I spent a fair bit of time wading through the British Medical guidelines on asthma and it's well worth it.
Any way. How I understand the "reliever" eg Ventolin, it works when your bronchiols are playing up or as a temporary "preventer" if the asthma's exercise induced.
As I found out, as an adult you don't get cured, your condition is managed. Since I hadn't used my puffer for ages the asthma crept up and sidelined me for a week. Back to the preventer (steroid puffer) for 2 weeks to settle it down and also had to take the ventolin as well. Lesson learned. So, back to taking a puff before exercise.
It's not a crime or shameful to have to take a puff. Plenty of world class athletes are asthmatic eg, Kieren Perkins (Aussie swimmer) and
Paula Radcliffe.