no high engine brake

[Swaid25]

I'm trying to find a decent price inline 6 on the road. I have my laptop and can get insite for a fair price. I for get the part# for the brake out cable on the engine harness I can just run thro the firewall. You right about the slow if any connection with my dash data port. The shops and people that do hookup just about always have to connect under the hood. But with the back pressure sensor I left it out and plugged up ran engine for about 15 minutes taking it up to 1500rpm every now and then. Waited for it to cool down took pipe back off and tried to clean it again but it was clean put pipe back on and new sensor in. I'm wondering if 1 of the new brake rockers blow a seal and it's only braking on 5 but all 6. I have no clue. Never had a problem with engine brakes b4 not even on my old 60s that had 1.8 million miles b4 a piston fail apart.