New, member, forum very helpful. Was installing new emergency brake cables, due 12-31-17. Removed floor mat 1yr ago, HPV still hooked up ,can feel pressure differential when moving arm, didn't know what the block did, do now. Will leave in in place, just do the mod on front brakes for now.Brakes were horrific, didn't dare drive it too far, right rear line look as if it had 99% blockage @ a protective plate on rear end housing, had a severe pinch. I have a 1989 Comanche Sport, short bed, 4x4, A/T, locked the front drive in, put a hose clamp on shaft, internally, after removing the vaccum motor , 40l engine, 189 k on the speedo. Installed a later mod radiator with fill tank. Putting new brake shoes & drums on the back. I'm 77yrs, don't plan to do any major mods, want something to drive % let the big trk stay home & rest, 2k, k3500 ,crew cab.4x4, diesel, 8' bed. Last year of the Classic Style. Thanks for the info here been a great help. Mossyjaw, N.C.