Question:
My friend told me that my amplifier will make more power if I use a lower ohm woofer or bridge them together to make a lower final ohm impedance. Is that true?

Answer:
You should never run a lower ohm load than what the manufacture recommends. By running a lower ohm load you are getting closer to a dead short which will produce more power but also more heat, current draw, and less of a dampening factor. This may work for a short time but eventually your amp will go into protection to prevent destroying itself or just burn up. Running your amp below recommended impedances could be compared to buying a new Ferrari and driving it all day every day with the gas pedal to the floor while towing a ski boat. Bad idea.