My 1999 Mercury Cougar is reading Bank 1 and Bank 2 lean how am I to fix this problem?

could be a motor mount or its not running on all cyclinders

P0430 code is(catalyst efficiency below threshold on bank 2)
P0420 code is((catalyst efficiency below threshold on bank 1)
P0306 code is(cylinder 6 misfire detected)

P01151 Lack of 02 switching meaning lean you will need to look for a vacuum leak or false air that has set off this code especially at the maf air duct tube and vacuum hoses

Replace your exhaust converter

Sounds like you have low fuel supply or a leak in intake system causing lean codes, check fuek pressure and volume first. Cat converter effeciancy could be caused by the lean codes, purge system sounds like solenoid failure, check for high resistance accross purge vent solenoid.

check the car for vacuum leak or leaks,all codes indicate a lean system which means too much air not enough fuel,get back to me if you need more help. Please rate my fix? Thanks Ray

might be number one fuel injector not letting enough gas enter the # 1 cylinder.

check the PCV valve hose from broke or there is any vacuom hose leak. make sure the MAF hose is tide and there is no air leak

Lack of HO2S-11 Switch, Indicates Lean.Right bank front 02 sensor. When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.In other words the 02 sensor is indicating lean and the fuel trim has reached the programed limit trying to correct it.
There are many things that could cause this like a bad 02 sensor,a vacuum leak,a leaking or contaminated fuel injector/s,a stuck open PCV valve,leak in hose between MAF sensor and engine causing un-metered or unmeasured air entering the engine,exhaust leak,improperly seated oil dipstick,stuck EGR valve.
Check PCV valve first if it is stuck open if you pull the hose off of the valve cover that hooks to the air tube between MAF and engine you will feel a strong vacuum pull there,normal you would hardly feel it.

code po420=catalyst system efficiency below threshold bank #1
code po430=catalyst system efficiency below threshold bank #2
from autozone online
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800a8b20