1988 Accord LXi/Compression Check, Plus.

What would "normal" psi per cylinder be for this high mileage engine? The problem: Around town at regular speed all is fine. It runs great w/no apparent oil burn. However, if I drive the car at or over 60-70mph for around 10 minutes when I decelerate AND/OR take off after a stop I often get a "machine-gun rattle" followed by a blanket of exhaust smoke so thick cars behind me disappear. Once I'm back to speed everything is fine again. Til next repeat.
Friends have told me it's everything from "piston slap" to a faulty (Midas) muffler that's backing up. I thought a compression check would be good for starters but I need some good advice on how to pursue. Thanks, Ray.