One of those people is me the big bore can work on the flats rather well but on the hill they have a bog for some resone :shrug: This was not only found by me but buy kim @ k&t and lynn at L.C. where we all run over 4500 ft. Also the air desity is afected here at 5280 we lose .7 points of compresion and 1.2-1.3 points where we race at 8500 ft so yes a big bore pipe does affect Things. One guy had a .104 methanol jet with the power jets 2 turns in, in his 10mm cub try that at sea level and watch what happens