+6 over-enchanted Armor Set Bonuses

Over-enchanted armor sets will give various bonuses. The following rules apply:

• all items of a armor set must be enchanted to +6 or higher
• only items that belong to an armor set must be enchanted to +6 or higher,
  eg. Plated Leather Set = Plated Leather, Plated Leather Gaiters, Plated Leather Boots
• the whole armor set must be unsealed
• rare armor items will not give the bonus

Heavy Armor Set – increases PDef and MP Regeneration

• D-Grade: +25 PDef, +1-2 MP
• C-Grade: +38 PDef, +2~3 MP
• B-Grade: +44 PDef, +2~3 MP
• A-Grade: +50 PDef, +2~3 MP
• S/S80-Grade: +68 PDef, +2~3 MP

Ligh Armor Set – increased MDef and Evasion

• D-Grade: +14 MDef, +2 Evasion
• C-Grade: +20 MDef, +2 Evasion
• B-Grade: +24 MDef, +3 Evasion
• A-Grade: +27 MDef, +3 Evasion
• S/S80-Grade: +33 MDef, +3 Evasion

Robe Armor Set – increased PDef and Weight Gauge

• D-Grade: +16 PDef, +30% Weigth Gauge
• C-Grade: +26 PDef, +30% Weigth Gauge
• B-Grade: +28 PDef, +30% Weigth Gauge
• A-Grade: +32 PDef, +30% Weigth Gauge
• S/S80-Grade: +38 PDef, +30% Weigth Gauge

Note;
MP Regeneration is per tick while standing not actively engaged in combat.
The PDef and MDef bonus gets added on top, aka it will not be affected by buffs.

source: http://tw.myblog.yahoo.com/l2_friend/article?mid=16873&prev=-1&next=16723