Marcus,

I see that the engine in the photo is the bare head, older model.
MVVS may have made some design changes, which get the engine on-the-pipe at a slightly higher RPM.
I believe your new engine has the blue anodized head and prop driver.

The #3241 tuned silencer is supposed to be effective from about 17,000 RPM to about 20,000 and more.
If your engine is not capable of getting to 17,000 RPM on its own, the tuned silencer will not help it.

The prop on the engine looks like an 8x4 MA. This engine runs better with a 7x6, or a 7x5.
Try using a slightly smaller prop. When it gets on the pipe, RPM will go to around 19,000.

Changing to a slightly smaller prop could raise RPM just enough to get it on-the-pipe.

Since this pipe is unadjustable, you cannot lengthen it to allow the engine to get on-the-pipe earlier.
The situation you are describing resembles a pipe-too-short situation. All you can do is to reduce the load.