My AC not cold on 80,000 bug, causing erreactic engine power when turned on

What is your question?

I just purchased a 2004 beetle from an individual and we noticed afterwards that that ac was causing the bug to have irregular power when driving 60 mph. After we turned off the ac, it ran fine. The compressor is stopping and going. I recharged the ac today and it ran cold for a while, but still cause irregular power. Could it have leak or worse, a bad compressor?