So I bought an 01 frontier SE king can desert runner. Great truck. Service engine light came on and most of the time it stays on. I wasn't aware it substituted the check engine light. It suddenly started kinda stuttering while I'm driving. It does it more when I get closer to 50mph and worse when faster. Rpms are fluttering more and it sometimes bottoms out but doesn't die. Read the code at O'Reilly's and it says thermostat. I'm no mechanic but I'm not sure the thermostat will make it do this. It seems more like bad gas or misfires. Can someone help please?