Dirtbag - modulation affects delay time?

[handlefras]

Hi guys,

I'm busy tweaking my Dirtbag to my liking (and to closely match my big box DMM). It does have some component mods and is running MN3008s on double delay boards. It is running on 14.8V, powered by the Road Rage. One strange thing I have noticed is that increasing the modulation (turning the knob clockwise) has the effect of decreasing the delay time. This is especially noticeable at the max (500ms) delay setting. Removing the modulation chip (TL062) makes no difference (apart from removing modulation).

If anyone else, who has built the Dirtbag, is experiencing the same phenomena - is there a solution? 
I'm already considering reducing R55 to 1k, but realise this won't solve the issue.

[handlefras]

After some more research I realised my DMM does display the same phenomenon when adjusting the modulation control. It just isn't as pronounced. I guess this is to do with the pot taper or something? Anyway - can someone suggest the components to tweak in the Dirtbag circuit to reduce the modulation depth? I really only have a use the first 1/4 of the pot's rotation, the rest is far too 'seasick' for my needs. Should I be simply looking at subbing the chorus/vib caps (C36 and C37) for lower values? Or should I swap out the mod pot for one with a different taper?

Thanks