I have run stage II's, Jammer 4s and now Supermentals on my stock 6 speed clutch. It has been bombed with ddIIs since 50K miles. I have 100K now with 125hp injectors for the last 25K miles and it has never slipped once. I don't tow ( at least nothing over 5K) but I do hammer on it pretty regularly.
Do you tow? If not, go as big as you can now, 'cause you're gonna want more real soon. For your money, I would suggest a set of jammer tips. I enjoyed mine but sold them to a friend. I regret getting rid of them, but I was chasing another problem at the time and thought it might be injectors. Turned out it was something else and my buddy got a sweet set of Jammer 4s out of the deal.
I think BD has tips as well. Some other members might chime in. I just try to post on my personal experience so I won't comment on other injectors.
The stage II honed injectors I ran were nice but I grew out of them REAL fast and wanted more after a couple of months. If I were hauling heavy, I would have stayed with those. They ran nice and didn't get too hot.
As far as mileage, I have gone from 16. 5 stock, to 18 with ddIIs to 20 with Jammer 4s as well as supermentals. I'm sure a timing box would get me a little more, but I'm happy with this for now.
Jason