should've done the uppipe with your header. taking the header off is 1/4 the ordeal. manifolds are cast iron so that they can hold heat better. heat = velocity = spool. in fact, i'd would rather have someone make a one piece cast iron manifold, instead of steel. i think that heat retention outweighs the penalty of weight. IMO of course. oh, and i bought my O2 sensor socket from autozone for $14 after taxes.

 

answer is YES....do the uppipe mod the same time you install the borla. it will be hell to pay later if you do decide to add an uppipe. plus I found that the borla alone was not totally unleashed until I installed my HKS uppipe this weekend. it is VERY restrictive. and if you wanna put it on later, you will have to remove the borla again anyway. if you want complete instructions on installing the whole deal I can give you the website we used to install mine. TRUST ME ... it's worth $150 and the time for that uppipe, plus that will unleash the full power potential of that header and you'll be done with one of the most time consuming mods (uppipe). took us 7 hours.