Im building a turbo manifold and I was wondering if anybody is having a problem with placing the external wastegate flange on a single runner, instead of on the collector. It would make cutting and welding a lot easier but just worried I will end up seeing boost creep

 

you should be taking it off the area where all of the exhaust gas collects but that is not always an option i have seen instances where the wastegate placed one one runner has caused a creep

 

If you have a standard 5 bolt turbine housing, get a flange with the internal WG hole. then weld a piece of pipe and a WG to the end. This is simply the most correct way to do it.

Otherwise, the best way is at the very bottom of the collector where the exhaust gases are all "shared". If you have a log manifold, directly over the turbo seems to work best.