95 safari idles and run rough

I have a 95 4.3L that is running rough, no codes. After a tune up it still ran the same "maybe some better" but still not good. I had it checked at a garage and was told that the #4 cylinder had low compression. It has 148,000 on it and it sat up for about a year befor I started driving it again. That is when the problem began. Could it be a problem with carbon build-up or making something stick? If so what can be used to clean the carbon out of the engine? Thanks for any help on this problem.