My truck(the 04.5) and one of my customer/friend's truck(05) are almost identical as far as performance mods except for the following. His truck has the latest version SC-V (mine is about a year older),TTS lift pump(mine FASS),4.56 gears(mine 3.73),39.5" tires(mine 33"),and a PPE EGR delete(mine finger stick and blocker plate).

The problem is that his truck will run rings around mine,even with the larger tires and slightly less overall gearing. His will smoke the tires well over a 50 feet without power braking(5lb boost launch) and pulls so much harder when traction is finally acheived. My truck almost feels like there's something holding it back,especially in 1st-3rd gears,it makes all kinds of noise,but doesn't seem to accelerate as quickly as his.It won't spin the tires on take off and barely hazes them on the 1-2 shift.Top end performance is not bad,but not as good as his truck.

Boost levels seem the same on both trucks,I'd say within a few pounds. Fuel pressure is good as well,his truck will actually limp the motor on long full throttle pulls with the PPE on kill and the VA on 90,where mine won't on the same settings.I've driven both trucks back to back on the same roads and can tell a huge difference. I thought it was me at first,thought my Seat of the Pants Meter was broken. After some side by side testing I know for sure his truck is stronger.

I'm going to send my trany back to SC and have it gone through and updated just so I know it isn't the problem. Any other places I should start looking? Could the turbo be hurt and still showing good boost numbers?

Sorry for the long read,I just wanted to include as many details as possible.
Thanks in advance,Bill

first thing that sticks out to me is the gear ratios.. he is going to spool up faster and accelerate faster even if you have the exact same mods done.

His truck with 4.56's and 39.5's has a little less overall effective geraing than my truck does with 33's and 3.73,s. All other things being equal mine should my truck should accelerate faster than his.

Gear ratio to tire size is almost identicle. 33" with 3.73 and going to 39.5, the new ratio would be 4.46. So 4.56's would be pretty close.

I guess I had my figures backwards,did them in my head kinda quick. With the figures you came up with his ratio would be about 2% lower than mine. Thanks for settin me straight.