Mina siad "what needle are u blokes talking about, how about a proper explaination please. "
Sorry Mina only picked the question up today....
In my case. I dont know if the standard needles had grooves around the top to raise and lower the needles or not. Sounds wierd if they didnt but.
Aftermarket needles generally differ in the taper, that it the original may have had a constant taper but a/m needle may be "flat" in the middle part.
IF you think of it as a "tap" that allows the fuel through it may help.
IF I had a bit of paper it would be VERY easy to explain.
ANYWAY, my input is that Dave Holdforth at Sydney Dyno (who should know as he is a dealer) said that Dynojet had a (large) batch of needles come out that werent smooth but rather notched down the taper due to faulty machining. After a time they actually "filed" the jets out !!!!!
SOOOOO if you have ever put Dynojet needles in and over time it got "fluffy" it MAY be the cause.