I can get a pretty good nod going if I take(in this order, orally unless otherwise denoted):
400-800 mg Cimetidine - (Tagamet)
50-100 mg Diphenhydramamine - (Benadryl)
Smoke some nugs while you wait 20-45 mins. (enough to get high but not blasted)
2-4 mg Clonazepam or Alprazolam (Klonopin or Xanax, Could be any benzo really, but these two work best for me, personal preference)
2-4 mg Suboxone - Insufflated (Substitute your usual dose or a very small dose if you are opiate naive.) Remember, with bupe, less is more. It's agonist properties are more prevalent at lower doses.
Sit back and smoke some more nugs. You can take more diphenhydramine now, it'll definitely help with the nod.
Adding muscle relaxers(Carisoprodol or Cyclobenzaprine, i.e. Soma or Flexeril), or some DXM with the other potentiators, can cause different/ more effects. Grapefruit juice would help as well.
This isn't really anything like heroin, ie no rush, but a little concoction I've come up with since I've been on bupe. It gets me high and can be some substitute, or at least calm the craving when I'm really fiending and can't interrupt my bupe maintenance.
BTW The whole blood brain barrier thing makes H totally kick morphine's ass. If you want to do drugs, there is absolutely no substitute for IV heroin. Maybe a speedball, but that's an entirely different topic. For me, H is where it's at, my one true love.