hissing noise from cylinder head

[newscram]

now i have puffing from the exhaust but when i rev the engine i can hear a hissing noise from the cylinder head and the engine smels funny
when riding it i can do about 23mpg wooooooo but it is dead slow to accelerate it never used to it used to accelerate pretty fast

btw i did the other ost called problem with exhaust

[sharpmagna]

leak in the head gasket? take a piece of tubing and hold one end to your ear and the other move around the head. The tubing will act almost like a stethescoe and will amplify the noise. maybe you can trace it to the leak.

[storysunfolding]

could be a cylinder not firing