I did a quick check and compared VOO (SP500) versus VTI (total market) and they have an equivalent performance over the past five years (within 0.20% gain), VOO didn't exist ten years ago and missed the last big crash. Both hold the same top ten holdings with the slight less weighting for VTI that one would expect. This may be harder than you think.
Over time, it's nearly impossible to beat a diversified index fund with any other strategy.
Market timing is bad for your money and your sanity.