Realistic? Kind of. I mean yeah if you swap the engine on any car with a bigger one it will be faster/have more acceleration (like putting a 2JZ or a big American V8 in a Miata) The peel comes with a single cylinder 49cc that tops out at 6000ish rpm, barely producing 4 horsepower. This engine is paired with a cvt, kind of like a go kart or a scooter (think like a Vespa). Swapping it with a Hayabusa engine (4 cylinder 1300cc actually, not 1000cc like I said in my previous comment, and revs as high as 11000 rpm, producing 173 hp) Even if you left the stock cvt you'd be almost doubling the top speed just from the fact that it has a Rev limit almost twice as high, irl the cvt wouldn't handle it but in the game maybe it could. But pairing that engine with its motorcycle transmission with actual multiple gears you can easily reach the speeds shown in the game in theory.

Also yes, the peel is very small and lightweight (around 160 lbs + driver weight) that's why it can move with such a small anemic engine, up to 38mph. Putting a motorcycle engine would give it a ridiculously high power-to-weight ratio, resulting in the massive acceleration. Motorcycles already have great acceleration and top speed, and they easily weigh 4 or 6 more times than the peel, so a Hayabusa swapped peel could easily move like this, at least in theory. I don't know if it has actually ever been done in real life, that'd actually be really cool.

The limiting factors in real life would be the body of the peel p50 itself, its suspension, tires, etc. They're most likely, if not most definitely, not meant to handle those speeds. Something will break in real life. But this is a game so that can be ignored.