I believe you would be very happy how the 1. 5's perform in your stock 08.
Here is an example of 1's in a stock 07. He has a South bend and an exhaust. He has stock turbo and and lift pump. Smarty on SW level 3.
http://us5.campaign-archive1.com/?u=d9444d3c8d721c9ce14c27a30&id=afc6e271f8
Kurt claims he gets 2 mpg and sometimes 3 above what he got with stock injectors. He is rather happy with his combo.
Here is a dyno number with 1's and a Jr on level 1.
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With a 6. 7 you would run 1. 5s.
http://smartyresource.com/bbi-injectors-07-12-stg1.5.aspx Although capable for the big power one can also tune these, just like the 1's to be used at a mild power level. There are those running the !'s around with 300 rwhp worth of tune.
There are several sets out there for the 6. 7 trucks. Here is a testimonial from Russell T, who has an '11'. No, Russell's '11' is not stock.
http://smartyresource.net/forum/showthread.php?18-BBi-Testimonials
I installed a set of BBI 1. 5's in my Early '11 6. 7 at about 18 000 miles, I have slightly over 20 000 miles on it now.
Before the BBI's my fuel mileage was 10 mpg hand calculated on a good day highway driving reasonable, with a mix of in town/highway driving I averaged about 6/8 mpg.
The biggest kick in the balls was when I hooked onto a trailer, flat deck hauling 3 sleds, 3000 lbs maybe, mileage would drop off to 6/7 mpg on the highway at the very best. I once hooked on to a 38' fifth wheel camper for a short 100 mile haul... would have been cheaper to charter a plane and stay in a hotel.
So, In go the BBI's, immediately I gained at least 5 mpg at the minimum across the board hand calculated... . and I didn't have the big drop in mileage while pulling a light trailer either.
These numbers are not exaggerated at all, I have hand calculated 18 mpg highway only at 65 mph... . mind you this is in ideal conditions, flat ground, no wind, no load, etc. where before it was 10 mpg max in the same conditions.
This is all on winter fuel.
On first start up after install the idle was noticeably smoother, at highway speeds the engine runs way quieter and way smoother, (I had bad injector noise with the stock sticks even at 15 lbs boost cruising down the road).
I usually keep the Smarty on Level 5, I've tried levels up to 9 and no injector rattle or noise at all with the BBI's.
I haven't seen above 1300 degrees EGT's yet, mind you the load percentage gets less and rpm's rise as I put my foot through the transmission.
The turbos light instantly, very little smoke, and no chance of snuffing out the chargers with too much fuel off the line.
I can't say enough good about these sticks without sounding like a poster boy for BBI. Definatley worth the money IMO.
I had the deletes, twins, etc in the truck already, there were no other changes made when the BBI's were installed and I've owned the truck from new. I keep a close eye on fuel mileage, the whole purpose of this build is to see what kind of mileage increases I can achieve, I still have alot of testing to do with different Smarty levels to see if there's anymore in it the way it sits. Next to go in is a Colt Cam and some valve springs, see where that takes me, then a Free Spin hub kit for the front diff.
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2011 Dodge 3500 Dually Crew 4x4 Auto LongHorn, BBI 1. 5's, 64/71/14 over S400, Smarty, Fuel Lab 200, etc.
I hope you find this of some interest.