Jacked69 -
I'm in the same boat as you. I just bought an OS 91 Surpass and did some research into smoke systems as well. I went with a [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXGVU1&P=ML]
TME SmartSmoker[/link]. I haven't used it but from all things I read it was quite reliable and very competitive for pricing compared to the Sullivan brands: around $100 (ave. price) I went a bit higher in quality as this is an investment for me not a toy (I plan on using it in a 28% Extra in the coming years).
As for the 4-stroke/ 2-stroke - from what I know your best bet is a 4-stroke because they produce more of the heat you'll need to get a good smoke cloud: so i've been told. But the bottom line is - the more heat, the better smoke - regardless of engine type. Also, how you install the smoker to the engine can be done with a [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLDR6&P=7]
Smoke Muffler[/link] which pre-heats the smoke liquid.
[link=http://www.tmenet.com/smartsmoker.htm]
TME's website[/link] has great info on how to install and use their product (better then the others), that's why I went with them. But again, I haven't installed mine yet - it's my winter project.
Visit [link=http://www.controlchat.com]Control Chat[/link]: For the new and aspiring rc airplane hobbyist.