H1b visa stamping - Need client letter or not if I am an US employee?

I was working on H1B visa for company A and got my H1b transferred to company B in 2012. Company B is a consulting company headquartered in the US and I am an US employee since I am on their US payroll. I want to go to India now for personal reasons and I will have to get my visa stamped on my way back to the US. Do I need to carry client letter for visa stamping? I was told that I do not need one since I am not on the Indian Payroll of my company but I am on the US payroll. So, I do not need a client letter? Please advise. Also, do I need to carry the approved H1b petition that I got from Company A prior my visa was transferred to company B. I have both the approved petitions (original H1b approval petition from company A and the approved H1b transfer petition from company B), I work in the EC model