Do the "Power Boxes / chips" really work?? What is the best option?? any\nrecommendations would be very helpfull. I want to upgrade for better\ntowing power not to just go faster.were you satisfied with the results??\nany side affects??( 2002 HDI 110 estate). are the boxes/chips\ninterchangeable or is it a case of individuality with each item?? thanks\nin anticipation.