I suggest that you try the following after disconnecting the battery:
1. Replace the fuse on the OVP relay, it should right on the top, it may be blown, or just bad contacts. You may not have to replace the relay.
2. Use Bosch Copper Spark Plugs and not platinum, they do not work well in smooth idle or acceleration.
3. If you can find BG-44K Fuel additive, it is similar to Techron but is triple the potency. You can only buy at some GM or BMW dealerships. You add it yo your tank and then fill it up with premium 93, so that it mixes well.
Hope this helps.