8-C1 from beginning to landing after the warp box: 142
Estimate of how long getting the power ups is: 5
length of 8-C1: 142 - 5 = 137
using P-Wing: 9
Time saved by using P-wing: 137 - 9 = 128

Getting 2nd P-Wing in 8-6: 63
Spare time: 128 - 63 = 65

Time for 3 extra coins: ~40
Net time saved: 65 - 40 = ~25