Maybe Wiswind can jump in here, but I think your year van has the electric IMRC. At startup, it may be going into "startup" position, and after the 171/174 repair, you may have eliminated the source of "amplified sound" from the IMRC and now operates quietly. Or, for whatever reason, you were just hearing the sound of the fuel pump presurizing being amplified up front and now after the repair, eliminated whatever amplified it.