2004 RX8 Stalling Issues

Hey guys i know that there is probably a thread out there for my question, but i dont have time to look around forever. I have a 2004 RX8 with 102,xxx ish miles. When i bought it from the guy he said that it would stall out well he was driving, he scanned the check engine light and found it was a random misfire (I scanned it myself and got the same thing). so i replaced plugs and wires. scanned and cleared code and CEL went away. Later started it up and found that it idles fine until it reaches operating then it stalls (everytime). However if i drive it and constantly give it gas it runs fun, no power lose. after it stalls out i can't start it till it cools down. I know that low compression is the cause but i compression tested it and it came out fine. I read that clearing the NVRAM can help with the misfire and stalling problem so i tried the 20 brake stomp. now here is my issue when i went to do it i turned the key to the on position (like you are supposed to) and stomped 20 times. now instead of the oil pressure gauge sweeping the CEL flashes.



What does that mean? The only code i get from the CEL is a U0155.



Any sort of help would be much appreciated!