Exhaust leak ?


At least from what I've seen, rich... It affects the scavenging of a tuned pipe, so you end up blowing fuel out the port and not sucking it back in from the back wave off the pipe. Engines without tuned pipes or even engine RPMS outside of the pipe target rpms might run lean from an exhaust leak. (So in other words, it COULD be lean at idle/midrange, and rich at WOT with an exhaust leak)
 


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