Yes, MUFFLERS is a Scrabble word!

Letter values in Scrabble US: M 3, U 1, F 4, F 4, L 1, E 1, R 1, S 1.

Is it a valid word?

MUFFLERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a tubular acoustic device inserted in the exhaust system that is designed to reduce noise
a scarf worn around the neck
a device that decreases the amplitude of electronic, mechanical, acoustical, or aerodynamic oscillations