burning smell on acceleration only

[sncboom]

Recently I get a "burning" smell on acceleration only on my '05 Nomad 1600. It's not noticeable until the bike is well warmed up and seems worse after the bike is restarted after stopping for a meal for example.It does not smell like fuel,oil,or coolant,or that acrid electrical odor. I removed the fuel tank and tightened all hose lamps even though I can see no evidence of any leakage anywhere and it made no difference. The bike runs very well and makes no unusual noises. I'm thinking maybe an exhaust leak? Anyone experience anything like this particularly the guys whose V&H pipes cracked? Where does that crack generally occur?
Thanks for any help
Bob