Boss also competed across 5 years in Indy Lights where he won the Toronto Grand Prix from pole position and had 4 additional podiums in Long Beach and Detroit.

Boss competed in the Formula Ford Festival at Brands Hatch in 1992 with Team USA Scholarship.

He won the Skip Barber Formula Ford Series three times, twice in 1992 (East and Midwest) and again in 1993 (South), becoming the first driver to win three Championships.

He competed in the Barber Dodge Pro Series from 1993 to 1996, winning races at Miami, Sears Point, Phoenix, Watkins Glen, and Reno.

Boss competed in the 2018 Porsche GT3 Challenge for JDX Racing achieving a best finish of 6th on three occasions, at Sebring, Mid-Ohio and Watkins Glen.