I will let you decide if you want to change the Chain or use the offset Key.
The lowest degree offset key is for 4 degrees of correction. However, you need to use the 2mm Methond for the calculation and look at the chate to be sure.
From what I have read Timing Chain Failure is most often caused by the Intermediate Shaft Bushing being worn to the exthent that there is too much end play in the Timer. Too much end pay ruins the Vacuum Pump and the Pieces of that fall into the Timing Chain and or Gears.
The other Vacuum Pump issues is on the Vacuum Pumps that had Bearings with a Plastic Retainer/Cage that held the Balls apart and or unshielded Bearings.
The Vacuum Pumps on the later models have a Steel Bearing Cage and Washers that limit the chance of bearings coming out.
However, on any of them if you hear noise from the Vacuum Pump Timer area it is time to stop the Car and get it towed Home till you can fiture out what the cause of the Noise is.
Anyone wanting more detailed info:
Repair Links
Fast navigation
http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html
http://www.peachparts.com/shopforum/forumdisplay.php?f=82
http://www.peachparts.com/Wikka/DoItYourSelf