Tillotson was primarily a small engine supplier. However, they did make some aftermarket automotive replacement carbs during the depression and during the war. Their only claim to fame was being a cheap alternative. If it has an adjustable main jet, you can try to adjust it out about 1/8 turn at a time and see if it helps top end power. I don't think you can really expect the top end performance. They had a good idle circuit and industrial engines could be idled down to where you could count the fan blades. If it were mine and it runs smooth, I wouldn't mess with it.
