My 97 K1500 w/259miles has some stumbling issues with low power. It seems like a fuel issue but I checked fuel pressure and its 55 psi at idle and maybe 53 psi when i rev the engine. Did not see any fuel on the vac hose on the regulator. The pressure did leak down to about 45 psi in about 60 sec. Checked engine vacuum ysterday and it was between 18-19 inches and very steady. Have not checked plugs or the cap yet but I would think if there were misfires due to them it would generate a code and there are no engine codes. What other things could cause this condition ? Someone mentioned a weak coil, is that possible?