I have not seen any dyno runs with the header only.

 

lots of folks quoting butt dynos on them tho... if anything the power or the boost response is able to be felt... i think that's enough to justify a couple hundred bucks.

 

Yeah, I went ahead and spent $220 hope to have it on next weekend. I should have waited and saved up for some cams, but oh well

 

i e-mailed them about the warrentee and haven't got anything back...

 

Waiting on one of these headers also. Have yet to see a 4G63 engine NOT gain response and or power with a decent header. And for the price. I will reinforce it with the TIG and get it coated inside and out. Using the stock O2 housing. Hoping it won't break.
The EVO 8 manifold is a great design. Especially compared to a 1g/2g manifold. Really think the key is a well designed collector and relatively small diameter runner tubing.

 

If you are running the OE O2 housing with the mount to block bracket, you will not need to reinforce it at all. I've beat the SHlT out of this combo for near a year without any issue.