Was doing errands in city traffic. I put in 98 fuel higher octane in small amounts for third time now. Things were going fine a few issues though and then I park car, walk dog and try re-start this morning. Crank crank crank, no start. Then, an ignite - but like was flooded and splutter splutter, then a bit more force revs till it was sort of smooth then I dropped to D so could move to a car park turn around where it stalled twice to get there. At turnaround stalled. Hood up, After a min more of crank crank pause crank crank, I got worried about battery discharge. Got it to go. I revved to 4k seemed to make it feel better. Then on way home every set of traffic lights got red. Then hit freeway and home. Freeway was fine. I noticed it missing a lot more though. And it has missed a lot since the octane change. The car rarely did miss, now misses. But at high speed is good, very nice power. When thumping accellerator I notice also vehicle kind of freeze on kickdown (auto), as though it is too much sudden ask for full power and it doesn't want to...then decides, 'okay' and accelerates. Any advice based on experience please give. Shall I go back to 89 /91 fuel?