MXR Vintage Script Logo Distortion+ louder?

[Death Super Mario]

I bought MXR Vintage Script Logo Distortion +.
In demos sounded better than Dunlop MRX distortion+.

I like vintage dist+ sound and tone.
Pedal has two problems.
One is that this thing only works on 9v battery.
This problem is easily fixable.
Another is that output volume is low when effect is on.
I need to put more gain on my amp to get it louder. Volume on the amp is louder when the effect is off. When effect is on volume is lower.
Amp is Orange crush 12.

Any recommendations? Can I make pedal louder?
I found great video on youtube.
https://www.youtube.com/watch?v=3aZbq2i-1Zg
Pedal is reissue.
I bought it from Thomann .
Yes I know that pedal in that video is modded.
Maybe It needs 12v from adpater for headroom.

[anchovie]

What pickups are you using? I suspect that they provide an output voltage swing way higher than the 0.3V threshold of the germanium diodes that hard-clip to ground in the vintage Dist+ so your clean sound is louder because the clipped signal is attenuated in comparison. You could add a silicon diode in series with each germanium (cathode of silicon to anode of germanium) for more headroom, though maximum distortion may not seem as much as before.

[Death Super Mario]

Pickup is passive egnater rail humbucker. 
Guitar Potentiometers are not very high output.  When volume pote is set full the output volume and tone is right. 

[Mark Hammer]

The "classic" unit had a 10k volume pot.  Replacing it with a 50k or 100k volume pot is verified to raise the maximum output level.

[Death Super Mario]

The "classic" unit had a 10k volume pot.  Replacing it with a 50k or 100k volume pot is verified to raise the maximum output level.

If I replace volume pot on pedal I get it louder?

[Mark Hammer]

Yes.  It does NOT increase "gain".  It does NOT "work" in every possible instance.  It simply loses less of the signal than a 10k pot does in that pedal in that exact same position.