Yes, but the only good results came from exhaust with diameter under 2 1/2" for 6 cylinder. so the pressure inside the pipe is higher and speed is possible do to higher temperatures and higher pressure inside exhaust.
All the gains that I had opportunity to observe was a full exhaust including mufflers and no cats.
with Headers only I had not observed any improvement and also no much gains with the ones with straight pipes (no Mufflers).
and in my opinion after see the results (Bad results) a very bad idea if you have ceramic cats and or cats with more then 200 CEL what usually caused the exhaust to fail miserably.
A good gain would come from Headers, middle section, and x-pipes with mufflers.
The mufflers only will be done with exterior coating.
I don't have any copy of the results as I was only able to observe them live.