My speedo and the one in my camaro does the same thing...Its got like a processor in it and it makes that sound...Its not anything to worry about..If its sticking the stock speedos tend to do that sometimes...Shwarmys is stuck at 3000 rpms like 24/7 lol
As far as the exhuast...It wouldnt effect the speedo...and I also asked a guy about the check engine light and its nothing to worry about....the sensors re setup to just notice stock exhaust flow what he said and if it changes a bit it does that..
Just get allen to fix it
2012 F-250 XLT/FX4 RCLB 6.7 Powerstroke
H&S XRT Pro Race(550hp/1100tq)/ 4" flopro exhaust/H&S EGT kit/SPE Full diff unlock/S&B CAI/H&S motorsports upcharge pipe kit/ DPF,CAT,EGR,UREA Deleted/Icon 3.5" Lift-Vs 2.0 shocks/PMF DSS w' Bilstein 5100s/Icon Adj Track Bar-upgraded steel bearing/RIGID LEDs/Kenwood DNX570HD w/idatalink maestro/Hertz5x7s/Memphis 12" slim/500.1 JL slash amp/Recon f250 led emblems