i just got my truck back from the dealer a couple of weeks ago after getting a new dpf and a drill and tap turbo cleaning . when i picked up the truck the e brake wouldn't work at all in the dealer lot . i got it out on the road and tried it a few times and it began to work . it is working fine now but has one small hick up once in a while at 1600 rpms . when using the e brake , it does just fine until it reaches 1600 rpm and the brake will cut out until it reaches 1500 rpm then works fine until the regular 1100 rpm cut off . it doesn't happen all the time , just some times . the truck is running great otherwise . i was just curious as to what could be causing this . anybody know ?