Shutting down

[jsando2]

My 240sx is shutting down by itself whenever , specially when I run it fast and after a while it just die on me. After troubleshooting and looking around tough I had it fix but then again it came back and still doing the same after I run it for a bit...Changed my coil ,checked all my spark plugs connections , wires, new spark plugs, new distributor cap, rotor and nothing, fuel filter, oxigen sensor, clean my MAF with MAF cleaner and is still the same. I changed my ECU not so long ago , mines was a 28 and I put in a 26 I don't know if this is the problem but it worked fine for the first couple of weeks. Is there a module or sensior that can make this happend? I'm thinking is a sensor but no sure what to look for. What else I can check withiout taking it to a shop?. I really think is that ECU that I just got and os going bad. Any info will be appreciated.