Opioids Opiate withdrawal and crystal meth

So.. Long time tweaker/opiophile (been on both for more than half my life). For the last many years, I've been an IV heroin user more than anything else. Any long-term junkie is familiar with what happens when you can't get your junk one day for whatever reason. I find that, lacking anything else, a big shot of crystal (or three or four or five) helps me through the first couple of days better than anything. I don't know if this topic has been previously addressed, if so my apologies. Reasons for the post are multiple: does anyone have any information on why this works for me the way it does? Is it just that boost in dopamine from the meth? I know a few people who swear that this is the most horrible combination they can ever imagine. Why would it affect me so positively and have such an opposite and negative effect on others? Anyone?

Here's a thread you might find interesting.

Amphetamines for Opiate Withdrawal