This is the official bill:
https://www.gpo.gov/fdsys/pkg/FR-201...2015-15500.pdf If you take a few minutes and read the proposal, you'll see that it applies to "heavy duty" highway vehicles with a GVWR above 8500lbs.
Page 40527 "As noted above, the exemption provisions of 40 CFR part 1068, subpart C, already apply for heavy-duty highway engines. EPA is proposing to add a clarification that the exemption from the tampering prohibition for competition purposes does not apply to heavy-duty highway vehicles. This aligns with the statutory provisions for the racing exemption."
So it's a proposed ban on setting up heavy-duty highway vehicles (eg semis and HD trucks) for racing, while clarifying that other vehicles can indeed be modified for racing.
"This proposed action would affect
companies that manufacture, sell, or
import into the United States new
heavy-duty engines and new Class 2b
through 8 trucks, including combination
tractors, all types of buses, vocational
vehicles including municipal,
commercial, recreational vehicles, and
commercial trailers as well as 3⁄4-ton
and 1-ton pickup trucks and vans. The
heavy-duty category incorporates all
motor vehicles with a gross vehicle
weight rating of 8,500 lbs or greater, and
the engines that power them, except for
medium-duty passenger vehicles
already covered by the greenhouse gas
standards and corporate average fuel
economy standards issued for light-duty
model year 2017–2025 vehicles"