closed loop means the computer is using the input from the sensors. ive been running open headers ever since i bent my y-pipe about 2-3 months ago and havent noticed any real change in fuel economy or other rich/lean conditions. fairly noticeable decrease in low end but the top end is improved quite a bit. the main thing is to make sure the o2s arent reading outside air if you run them open. usually you would want to have an extension of some sort. header install really isnt bad. the hard part is getting the stock stuff out. if you arent gonna reuse or sell the stock stuff some parts can definitely be easier to cut off then wrenching and breaking bolts.

 

Im going to keep the parts, just for the peice of mind.