Downpipe with best power output

[DiogoDC]

So I'm staying mostly stock minus the downpipe and maybe an Intake and getting bit tuned no use for an exhaust myself or anything o just want the downpipe since it has been proven to yield the highest gain and pinpointed as the most restrictive part
My question is which catted downpipe has an average of the highest gains compared to others?

Notice I say average everyone obviously has different numbers and results
Thanks in advanced guys been looking for days and I haven't found any topics covering this as of yet making any comparisons

 

[squiggy]

Full-Race or Ultimate Race are the best and most popular choices. Maybe Skunk2. They are 3" as opposed to all the others available. They will be comparable in power output. FR and UR are cheaper than Skunk2.

As far as actual gains, you will be hard pressed to find many people that just got a DP and before and after tune comparisons.