Hmm, lets see... clogged fuel filter, bad plugs/wires, flaky CPS, bad MAF, frozen fuel/ frozen lines, water in gas...
Since the methyl hydrate (ie -heet) seems to help I suspect you have water in your gas and it is freezing up.
The only other thought is a sticky IAC or possibly bad MAF. If the IAC sticks it may not be getting enough air to run very long. Since you say it smells like raw gas in the exhaust it sounds like its getting plenty of fuel, so that only leaves air and spark. If the air cleaner isn't clogged and IAC good then it must be spark. Check plugs/wires, battery cables, grounds, etc. and then go from there in the ignition department. Not overly familiar w/ the 88 GP but familiar with cars in general.
