When I had my 06 Apex, we had a similar situation, turned out to just be a loose clamp on the rubber boot from the turbo. Many of the problems I had with that coach were things that good old WRV forgot to tighten at the factory.
Jim and Sally & Rufus the Lakeland Terrier
2001, 40' Country Coach Affinity, towing a 2005 Ford Explorer Sport Trac
Carson City,NV, Surprise,AZ, Florence,OR