If you are getting skipping in the two smallest cogs in the rear, your cassette is worn and needs to be replaced.
A couple of other comments though...
1. How did you rejoin the two links you previously removed? SRAM 8 speed chains use rivetted pins which are not designed to be removed and reinstalled.
2. To size your chain properly, wrap it around the largest front chainring and the largest rear cog. Figure out where the chain would be joined to just fit this combination then add two links (1" of chain). That is the proper chain length and will never need to be adjusted.
3. I use whatever is the cheapest 8 speed chain that I can find. I think the last SRAM PC-830 chain I bought was under $10.