SU carb piston spring selection

[GT6boy]

Whilst ruminating on my ongoing mystery missing power issue with my engine- it occured to me that my carb pistons springs may be wrong? :-/
My HIF38 carbs have the big 2" piston springs, currently yellow 8oz. Am I right in thinking the fitting of lighter 4oz springs(the only lighter weight available) would allow for swifter piston travel, but then all new needle selections to suit?
I can't recall now why I settled on 8oz springs 4years ago incidently, but the Spit 1500 has the 4 oz springs fitted, and that has only moderately more cylinder capacity epr carb than my 2 litre in comparison.
Anyone else fiddled about with non-standard piston springs?

[Deleted User]

It was always recomended that you changed springs when changing air filters to K&Ns, i never found the springs made that much difference in changing them, oil however makes a big difference, try mixing your own oil.
I run a custom mix on my 1500, think its 50/50 2in1 and engine oil.

[ferny]

I put in the heavier spring (is it red or yellow?) when I put on the TR6 filter and put it behind my number plate. With old spring the piston moved too quickly allowing air in faster than the petrol could move, weakening my mixture and causing thr car to stutter. As soon as the heavier springs were fitted the problem went away.