For the last 3 years, my Windstar 2000, 3.8 engine has been making a [b]"rattling" noise, a "chain like" noise[/b], mostly when stepping in accelerator for more power, or when climbing hills, etc.

Dealer said to change fuel to 93 octane, [u]although the car manual states that 87 octane fuel should be used[/u], and [b]the noise has only minimized a little, but persists.[/b]

Had it analyzed recently 'cause the "check engine" light's on; dealer said something about [b]" Ports 1 and 2 of Lean System (?) are releasing air thru the Plenum " (???). [/b]

Also, during normal stop & go rides, when changing gears, the van [b]makes a short, "bumping" movement and hesitates[/b]. Can feel the "hesitation" on the break pedal, [b]like the engine trying or wanting to go off.[/b

Any ideas? Dealer gave repair estimate of $350. Is it fair?