Because Amped Up pushes the N64 hardware to its absolute limit (and beyond), not all setups will run it smoothly.
Once you have your base ROM and the Amped Up v2.9.2 patch, follow these steps:
We need to address the elephant in the room. You cannot just download a pre-patched ROM link from a random forum without legal risk.
Here is the rule: The patch (.bps or .xdelta file) is legal. The ROM is not.
How to comply: Search for "Mario Kart 64 (USA) ROM" (we will not link it here). Then, apply the Amped Up patch using a tool like Floating IPS (Flips) or Beat. This gives you a clean, playable "Amped Up v2.9.2.z64" file.
You can now play the patched file on:
Instead of the static 2D faces, v2.9.2 introduces 3D animated character models rotating on the select screen. You can now pick Koopa Troopa, who has a unique triple-green-shell ability, or Petey Piranha, whose massive hitbox is offset by incredible off-road speed.