I can now offer my driving impressions of the THS mounts having been out for a drive in different conditions - fast, slow, country road, city traffic, etc.
The THS mounts are very good, definately stiffer than INA/034 street density and not as stiff or harsh as the track density mounts, they sit inbetween them. There is NO increase in vibration or noise, the best way to describe the THS mounts are tight and sporty. Gearchanges feel smooth, everything feels nice and tight without being harsh at all. Even with the Superpro void fill bushes in there is no vibration. Overall I give the THS mounts 9 out of 10 - great for all but the harshest of driving styles.
For 99% of us I'd say the THS mounts are spot on, even for the odd trackday or 1/4 mile.
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I've never tried Vibra Technics mounts so cannot comment on them, they are very expensive though compared to the THS mounts, almost twice the price.)
Better still, if you use the code SCNFR3CMP you'll get £49 off the price of all 3 THS mounts, mine cost £163.63 including VAT and delivery for all 3 mounts!
IMO INA really need to upgrade the front bush of their street and track density dogbone mounts - very soft indeed.