ACE issue Oppty Visibility Issue

Hello SAP CRM experts

I am facing one Opportunity visibility issue

One User Id is shared by more than one user e.g user id test-01 , Users assigned x y z

among these users x is directly assigned to user id test-01 and rest y & z are sharing users.

all x y z are using same user id and password to login

whenever apart from x .y & z is using user id and create transaction like lead oppty quote .there names comes in partner functions

like Logged in user by default will x (cause he is directly assigned to user id ) and Employee responsible will be y or z whoever using that id to create transaction .Y & Z have to manually choose there names from partner function employee responsible.

Now these x y z has reporting manager also Reporting mgr has different user id where only he is assigned to his id

e.g if reporting mgr is P user id test-02 ,then P is directly assigned to test-02

and x y z creates any transaction that will be visible to P in his login .

Now issues is whenever any of directly assigned user is removed from user id (reason being x resigned from compnay so his emp code n detaisl r deleted ) e.g if x is removed from id and

Now user Y is assigned to User id test-01 .

Y & Z both are not able to see there previously cretaed transaction at all

However these transactions of y & z are visible to his manager P in his id test-02

if i try to find transactions of Y Z on Production GUI , CRM Production show all user transactions

So guys plse help me on this issue its Urgent (Points will be rewarded)

we are using sap crm 7.0 and it is in integration with ECC 6.0

We have implemented ACE Functionality