If fuel is flowing out of the carburetor or exhaust, your float is not properly adjusted or the float valve is not sealing.
If it starves for fuel after running it hard, you may be getting a vacuum lock on fuel flow due to a blocked gas cap vent. This would also explain why you have flow issues when using a fuel filter.
Once you have the fuel issue fixed you will need to change the oil because I'm certain tha gasoline got past the rings and is mixing with oil. Run the buggy for half an hour on the changed oil and then change it once more to ensure you are running oil that is not contaminated.
2006 Tank Urban Touring 150SE
6" intake plenum, 1.5" UNI filter, K&N precharger, 130 main jet, NGK Iridium IX CR7HIX spark plug, MRP yellow adjustable CDI, Orange high output coil, 14Ah sealed battery, 2000 RPM red torque spring, Koso 115mm variator, Dr Pulley 12g sliders