dying problem 90 laser rs

[Gvr-4]

Hey everyone, I just bought a stock 90 laser turbo and I have this goofy problem. It will drive fine and then all of a sudden it will just die. Ill try starting it a few times it will run for abit then die, but then eventually it will start and run again. also when it dies the rpm needle will swing up and down while its dead, I did some research and people said that it could either be the ecu or the cam angle sensor? but I dont want to buy anything on till I find out what it could be. has anyone else had this problem? thanks.