I find the BoostMASTER 30 working well in my car; will upgrading to a Top Fueller give me more power?

Generally it will never hurt to ‘over spec’ with Broquet, unlike chemical additives where there’s always a danger of engine damage caused by ‘overdoing it’. The Top-Fueller will always show an improvement over the smaller units, only if the smaller unit used wasn’t optimal for the car. With the in-line units, the manufacturer has a certain ‘formula’ for calculating the ‘rough optimum’ based on horsepower output. While you may not see double the improvement e.g. putting a Top-Fueller unit into a Toyota Corolla vis-à-vis a BoostMASTER unit, you may still see an improvement in overall fuel efficiency. Remember this increase is not linear and tapers to a plateau.