Ron Garret wrote:

A couple of related questions. You'll want to get your southern
California approach plates out to follow this.

1. The preferred tower-enroute IFR routing from VNY to SNA ends at SLI,
but SLI is not an IAF for any approach into SNA.

SLI is a feeder fix for the ILS 19R; i.e., there is a published route and
altitude to MAAGG, then to the IAF.