no,compression is compression, unless your trying to compress a liquid (that's one thing we thought it might be). also you said it pulls fine sometimes. there is no compression build up other than the compression stroke. at the first sign of the hard pulls remove the plug wire only and see how it pulls. then post your findings.
i remember 20 years ago i worked on a techumseh that had 2 counter balance weights and gears that broke and locked up the engine. i don't know if your engine has that but that is absolutly the last thing to be checking. try all the other things we all suggested first.