Yea, thanks for advice. The problem is that the engine was re-built (there are 2 mechanics, one is building hardware only but mapping is done by other guy, it had previous map by this same guy but the engine lost compression etc (not by his fault, engine was weak long before it), valve was damaged and sparks were terrible etc. So I got new valve, piston rings, ported head, lightened flywheel and lightened crank pulley, etc. And then got mapped by this same guy I used to go to, and that was all awesome. Then there was engine light and idle was shit and I had that problem while filling tank. Missfire again. Changed Ignition coils, issue was there. Changed sparks, issue still there. Changed throttle body, issue there. Changed MAP sensor, issue there. The only difference that I can say for now is that I don't see engine light flashing anymore. But I didn't drive car that much anyway, maybe 3 times last 3 days so who would know, maybe engine light will come back. Regarding the tank / venting valve / etc was not altered from what I know. So now it is either that or the map somehow. My mechanic for hardware is now away for holidays for next 20 days (the one which rebuilt the engine), and I the mapper is coming back from holiday soon and as soon as he is back we will check out the map. Currently I don't know what else I can do. I just show these messages you guys tell me, all the suggestions, I send them to mechanic to take a look. Until then, map will be checked. There will be 3 upcoming track days next week. I will skip them all... don't want to push the car while I have this problem. Do you think something can get seriously damaged even if I just drive it around town slowly?