Hi there,
to me that looks like the engine is not getting enough gasoline in order to rev higher and maybe something gets squeazed when making the turn restricting the flow.
When I replaced my fuel pumps, I routed the fuel hose wrongly and it was a bit constricted. It ran fine until I accelerated. Once re-routed, everything ok.
There are also 2 check valves that help to keep the pressure up and I believe they are only 13.50 or so each. You might want to replace those.
I believe the dealer has a contraption to measure the fuel flow.
Good luck

__________________
Reinhard Kreutzer
1987 420 SEL (126)