Reg: Performance issue after migration from Vb 6.0 to Vb.net 3.5 using tool

Question

Hi,
I have migrated an VB. 6.0 application into vb.net 3.5 window application using an tool called ArtinSoft.
Neither I have rearchitect it nor optimized the codebase.I have made as less as possible changes just to make the aplication run properly. Now I am facing the performance issue. Performance of the Vb.net application is much slower from  VB 6.0 application so our client is not ready to accept it. Now I need to optimize the codebase and may be I can rearchitect it upto an certain level.

Please help me on , what are the things I need to optimize when we do this type of migration using an tool. this is first time I did so.

please help me if someone has already done this type of migration project or similer activity.

Thanks
Akash Agarwal