Performance exhaust and k&n panel filter, fuelling correction

Hi guys I recently fitted a set of Highway Hawk fat pipes to my 2008 vl800 intruder the previous owner had already fitted a k&n panel filter. The bike seems to be running fine but I do worry that the bike is running lean. Can anyone advise the most cost effective device to correct the fueling.The exhaust has the lambda sensor fitted. Up to now the options appear to be power commander, healtech fuel controller, cobra fuel controller, and I was wondering if a boosterplug would work for my set up. I'm not chasing more power as I'm happy with the performance of the bike, but I am concerned if the bike is running lean I'm causing damage to the valves. I'm sort of close to the end of what I want to spend on the bike, so basically looking for the cheapest effective solution. Thanks in advance John

Hi folks managed to find a fuel controller waiting for it arriving from usa.