I've got a 2zz-GE powered Corolla. It's got a custom 2 1/4" open exhaust. Last fall sent the throttle body to MaxBore , he will bore & taper your TB to its maximum safe amount. While that was being done I pulled the intake runners & plenum and basically did a port match , mild bore and finishing. Nothing too drastic. Toyotas in general have well designed and fairly optimized intake & exhaust manifolds. Much better than pretty much any of the domestics, Hondas are pretty well designed also. So got everything back together , it definitely helped the low & midrange throttle roll on and response. Just had two short drives afterwards as it was time to get that car in storage for the winter.
The guy at MaxBore claimed he had yet to bore a 1GR-FE TB. He has done some previous generation Tacoma & 4Runner TB's. The 5th gen 4Runner has a composite (plastic) intake manifold so modification is not going to happen.
Next month should have a TRD air box installed. I'll pull the TB and see if it looks like much improvement could be made from factory. So I may be the guinea pig for this mod. Ideally it would be great if some aftermarket would design, flow bench & dyno an aluminum replacement intake manifold for the 1GR-FE.