Bud-- wrote:

Research done for the CPSC showed the purple wirenuts were generally not
any beter that other wirenuts and were worse than some others. As far as
I know they are the only ones UL listed for aluminum wire.

Inspect-ny.com reccomends a 3M scotchlok wirenut instead of the purple
Ideal 65 wirenut found at the Borg. These are about $4.00 for two in
NJ. I couldn't find CPSC approval for the 3M wirenut.

Here is how they reccomend pigtailing
http://www.inspect-ny.com/aluminum/pl2p12.htm

best thing to do is hire an electrician knowledgeable in aluminum
wiring repair.