If you’ve been working on your speed but you can’t quite seem to make it to the next level then you’re probably practicing incorrectly.
The key to increasing your speed is to push yourself slightly past your usual comfort speed level and practice short burst of speed exercises. Even at the risk of sounding a bit sloppy! This serves to build the new speed level into your muscle memory. Then, when you back off a notch or two on the metronome, you’ll find that you will be able to play faster and cleaner than before.
It’s kind of like taking two steps forward so you can take one “clean and precise” step back. Try it! But don’t allow your muscles to tense up at any time!