dmosley73

what's the most efficient route to gain some horsepower for my 2015 express 3500 6.0L, to ensure being able to tow 8k lbs with efficiency? would a programmer be sufficient or would i possibly have to consider a cold air intake kit? i know air flow helps intake and exhaust wise, but if you guys have any tricks you've learned, sure would be appreciated. Carvana is giving me a crazy number for my 2016 silverado 2500 HD, so i have to use my van until i get another truck. according to a local chevy dealer, he says third quarter he is going to get hit with an influx of trucks(due to computer chip shortage now and being behind),so i will be using my van majority of the summer until the supply increases, hopefully dropping the prices on new trucks. thanks in advance for any and all advice.

i have a 2016 silverado 2500 HD 6.0 gas engine with 27k miles. i have never had an issue with this truck, i bought it with new with 16 miles. took a trip yesterday and put around 500 miles on the vehicle. when i came out today to go some where, the truck wouldn't start. all the lights on the dash come on, when you turn the key, you can hear the relay under the dash, as well as feel the relay in the fuse block engaging. there is no click at the starter. battery has 12.8 volts and doesn't not draw down when you turn the key. snap on scan tool pulled codes p685 p686. both related to pcm power relay. is there a PCM power relay? where is it located? can i test it? i'm a total noob here but i've been doing my own wrenching for 30 years and any knowledge or assistance would be great! thanks