Yes good stuff - I think I'm getting it

...So practically speaking - a case problem...

I have not yet put in a new lower butterfly plenum on my DOHC. I have it disconnected.

When I am on a flat stretch of freeway doing about 70-75 on a windless day, (slower speed in headwind) my 4wd lights will start flashing. If I let off the gas and then step on it again to maintain my original speed - the lights will go off. Only to come on again over a short period of time or if I put a slight bit more load on the engine.

My theory is I have a vaccuum leak from the bad plenum, and this is somehow affecting the system. But isn't there less vaccuum at higher RPM's? So would it be a bad check valve?

I dont understand what the resevoir is doing either <img src="/forums/images/graemlins/confused.gif" alt="" />

Yes, go buy a plenum...somebody spare me $400. <img src="/forums/images/graemlins/barf.gif" alt="" />

I'm not willing to spend money, I'd just like some free answers <img src="/forums/images/graemlins/smile.gif" alt="" />