Blown Head gasket or intake manifold?

[Project77]

just had a 94 truck in the shop i work at it had blow by(white smoke) coming out of the oil fill cap the truck wouldnt idle had to keep throttling it. eventually we did a compression test and one cylinder had low compression while all the others were around in the same range. the conclusion was bad rings on the one piston which was allowing gas to get into the oil. sound like your problem? compression test is very important make sure all of the cylinders are in close range to eachother