The trigger points control 1+5, 4+8, 6+3, 7+2. Sounds like half of your trigger points are gunked up or have failed. Your symptoms EXACTLY describe gummed up points. When cold, you'll fire on 4 or 6 until warm enough for the oil to run off of them and get all 8 going. No money involved if you use an index card to clean them (NO sandpaper)!