850 thermo quad

Put few hundred miles on my car since back on road ..starting to have high idle after I get on her and do a few rips after warm up cruise, but she will come down to normal idle sometimes after a little bit ..also has hard starting after warm,have to floor gas to start almost like it's flooded.. runs fine if you just cruising around and she is strong and has no misses on cruising or running it hard..could I just possibly have picked up some shitty gas?? Been using 93. And did have to put 87 In her but started doing before I put the 87 I. Anyway?? thanks guys!!