no it's really noticable. like you depressed peddal or there are some missfirings.

 

might wanna check on the plugs. samething happened to me this summer. i put in new plugs, but apparently the car didnt like them. i couldnt figure it out. i ended up throwin a CEL, brought it into Hyundai and thats when they told me the plugs were no good.

 

I have no CEL

 

auto-transmission? May be trying to drop RPMs putting it in gear. vacuum lines, fluids?

 

I have manual tranny

 

This sounds like the famous "Flat Spot" in our ECU programming.

 

but it happens only when there is less than 1/4 gas in tank dunno.gif

 

Most twin cam engines have what is refered to as "twin cam surge" which is less noticible in an injected car than a carbed on. You can hide a lot with good fuel control. Anyway, most twin cam engines will have a flat spot about three quarters of the way through the powerband before picking up again at a higher rate. I think it probably has a lot to do with the flow dynamics of the head.

My Tib has it, My Fiat has it, just about every twin cam engine I have driven has it to an extent.