The clearances and dimensions vary on stock cars, but when parts are changed, these clearances can get worse.
The biggest problem we have had with downpipes over the years is when a non-stock turbo is used. We even had to exchange some aftermarket turbine housings as the bolt pattern was WAY off. I would guess a 5857 turbo does not use a stock Garrett turbine housing?
In your case there a 2 remedies to try before hammering the DP.
First, open up the 4 mounting hole in the DP flange. A little movement there will give a lot of movement at the frame.
Second, if the first does not move it enough, then remove the turbo and elongate the 3 mounting holes in the header/turbo flange. This will allow you to "rotate" the turbo so the DP can move up and down.
I know this can be frustrating, but remember you are modifying a stock car, and it is not unusual to "cut-and-fit" for aftermarket parts to work in that situation.
Ask the guys that build race cars what we have to go through most of the time! :biggrin: