Most People do not realize the front coil spring air bags on the CHEVY P-30 chassis are Chevy installed and are REQUIRED to be functional and aired up to get the front suspension to track and ride correctly. As to heavier aftermarket front Coil springs. That may be a replacement instead of using the Air bags. As someone who has ACTUALLY driven hundreds of P-30 chassis from 1979 to the early 90's, the Chevy factory set up is fantastic. The handling is just like a car. Do NOT confuse the P-30 with the suspension on the Workhorse chassis in handling. Doug