Evan Poulos

I’m a tad late to the party, but I’m having the same issue as OP. I recently purchased a 2015 Silverado LT Extended Cab that the previous owner modded. It has MSD coils, upgraded spark, a Jammer CAI, and I have no idea what else. It shifts and sounds aggressive, however my 1st-2nd shift happens around 25-30mph. Trying to find out how to reverse search what was done to the truck somehow