Misfire when you accelerate

I have a 2001 Chevy Astro that has 230,000 miles on it. I been having a misfire and chugging going on for a while, so I took it to a shop and the mechanic said it need a map sensor so I replaced it, which did not fix anything. I took it back to them and they said I needed a tune up which I had them do. Replaced fuel filter, air filter, distributor, plugs and wires still nothing changed. Paid $560.00 for repairs still no change. Took it to a second mechanic, he did a compression test and some others fuel pressure, electrical and he found one of the wires that the first mechanic put on arcing so he replaced a couple of bad wires, but still nothing changed. Then he told me I needed a crack sensor and a ground wire fixed this was done also. The second mechanic said that I should just get rid of the van after charging me $532.00 repair with no avail.

I am at the end of my rope with this now and would like to get some help if anyone has had this problem. Thanks for your help.