2002 nissan sentra ser specv strutering at idel?

I used a mixture of e85 and 93 octane for two weeks. I never went over an e 40% mixture. The car now developed a stutter at idle. It also stutters in first gear when I an tacking off, when I turn the AC on and seldom at 3-4 k RPM I tried fuel cleaner and it only made it worse. I changed the MAF sensor and the spark plugs. No results. does anyone think I should do a fuel system flush or any ideas?