JAAY - read the entire thread (when you have a spare couple of days!!) and you will see that they have been dyno tested with good results.
I think I have found a way to get better results from them though. First of all, they should be ceramic coated, this keeps the heat inside, keeps the o2 sensors happy and produces more power due to the exhaust temp staying inside the pipe. Secondly, the mid pipes need to be modified or changed completely to have a 2" opening as this is the size that these headers are at the flange. The stock 2.5l mid pipes are 1.75" here and it creates a huge amount of turbulence and therefore restriction at this point.
The dent, will cause minimal if any restriction or power loss, its nothing much and normally just pushes the pipe into an oval shape anyway so you dont lose any flowing area.
Sam
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