I would try either Gene's or Bob1951chevy's ideas before changing the manifold gaskets. You need to identify the problem before you can fix it. If it does not suck in the oil or propane then look for another cause. Have you done a compression test?
Thank you. I will double check idle mixture and speed screws.......I believe they are ok. Thanks for advice on gaskets...my next project ! LOL Do I need to put any sealant, etc. on this ? Want to make sure I do it right the 1st time.