I Just picked up an 05 with the 4.7 vvti and the owner gave me maintenance records which shows they brought it to a private shop on 2 separate occasions.
1st time at 166k to replace Secondary air injection switching valves and intake manifold gasket. 2nd time about 6k miles later states they replaced air injection pump.
No check engine lights on currently, but I did notice a high pitch shop vac sound people mentioned in this thread. Anyone with more knowledge on this, do you think I should just do the bypass to be safe?
Should also mention this only happens at cold start, I noticed it because I added remote start, hard to tell from inside the truck.
I'd bypass it now before the valves get stuck in the open position. It's extremely easy to install if you don't need to install the plates. The kit is only like $50 so why not. I installed mine three years ago in about 10 minutes and I've been running perfect and passing smog inspections ever since.