I need pressure cooking help

I got a 5-qt. Kuhn Rikon pressure cooker recently and think it's great except that when I make things with thicker sauces (chili and curry) more often than not the bottom gets really scorched. I have to soak it with baking soda for several days and scrub scrub scrub before I can get it clean again. I think the problem is that when I'm getting it up to pressure I can't stir the food so it burns on the bottom. I have an electric stove with coils and I've tried lowering the temp. a bit as it's gettting up to pressure, but that doesn't seem to help. Plus, it just takes longer to get up to pressure, so it seems to defeat the purpose of having a pressure cooker. Also, the last time I made curry the burnt flavor permeated the curry and made it somewhat inedible. Does anyone else have this problem? I haven't purchased a heat diffuser yet, but I guess it might be worth a try. I appreciate any suggestions.