yesterday, i decided to take the Diablosport Trinity i have out of my Camaro, have the Camaro dyno tuned, and use the programmer in my Silverado. average fuel mileage was 17.0 mpg mix of city/highway. at 70 mph i was getting about 19-20 mpg on flat road. after i installed the 87 octane tune on my programmer, i took it out for some testing. i was getting 22 mpg at 70 mph! i ordered a K&N 63 Series intake; almost went with the Volant powercore, but i read on here and elsewhere the volant box doesn't seal too well and the K&N had great IAT, MAP, & HP numbers according to Jennabear's intake thread. i wanted a sealed box with a polyethylene tube because we get really hot summers here, i do a lot of highway driving, and it is also very dusty. also ordered Corsa DB Series cat-back exhaust, single side exit. i decided on the Corsa because of their "reflective sound technology" with zero drone while cruising and big sound when you stomp on the gas. i've had Flowmaster and Magnaflow on vehicles before and didn't like the cabin noise they created. i got the intake for $284 and the exhaust for $517 with free 2 day shipping from Amazon.com. not to bad considering the intake was $600 and headers/exhaust was $2000 on my camaro! my main question is: for those of you that have a similar combo (intake, cat-back exhaust, programmer with 87 octane tune) what kind of fuel mileage are you getting mixed city/highway, and also how much just on the highway? i also ordered the steering wheel w/ audio controls, Universal Home Remote roof panel, and Katzkin leather in ebony w/ dove tail grey perforated inserts and grey stitching. i'll post a new thread once i'm done with each thing!