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yep

I think I am better off using 65mm one, 70 looks too big for stock v6.

Depends on what your doing. I have used both. When I was doing a lot of freeway driving the 70mm TB was ace, almost no throttle required to cruise but then I changed jobs and it required a lot of stop/start driving. With the 70mm TB even a very small throttle application saw a lot of revs with a manual car taking off so I went back to a standard 65mm unit.

even with my 66mm its a bastard to drive, wheel spin just about every time when I touch it driving in the city.

yeah in the country its awesome. maybe I need to find a more local job in the country lol.

The V8 and Buick V6 throttles will bore through just fine at 70mm with enough wall thickness but yes they are getting thin and very close to the bearings for the throttle shaft have done a few and currently running one on my VS GTS I noticed a small gain in the 2000-4000rpm range but it felt the same past that because that is then the manifold becoming the restriction.

The ecotec throttle can not be bored to 70mm because you break through had one we tried on a mates lathe when we were doing the others and yes you break through had a look at a few that other companies do and a lot of them tapper down inside so both ends maybe the 69-71mm they say they are but as you get towards the middle they tapper in heard of a few that were done to 69mm with no tapper that developed cracks and holes after a few days use.