i have been reading alot about this topic.
1.They are exact design specs as MSDS.
People say knock off because they copied the design off msds.
2. Fitment issue. There is none when they go on the engine. The only fitment issue is the egr tube comes up short about a 1 inch short. You can cut the pipe and weld an extra piece of pipe and that problem is fixed.
3. The only thing is they don't come with mil's you have to buy them seperate i found some for sale for ford autos only for 25.00.
4. CustomCougars have these headers for 338 then add 35 for shipppig and 25 for mil eliminators and you have a set of headers and y pipe for about 400.00.
5.Weapn R' come stainless steel. Msds you need to get jetcoating or they will rust. (i live in michigan).
Overall i hear they are decent, but poeple don't like them even though they are the same design as msds. I think they don't like knock offs. But MSDS is 740.00 with shippind and jetcoating i'd rather spend 400.00 out the door and save 340.00.
Well this is my opinion and facts just look at
www.cougarcustoms.com for more information good luck!!