i would imagine that the volt meter can be swaped in place of the boost gauge. You would have to rewire the pins from the cluster so the new inputs wouldnt be from the PIM but a 12v source.
worse case the whole gauge cluster will have to be swapped out and the possibly the pin outs on the three plugs re arranged.
At least this is how it is on the 6th gen celicas... I have a 4th now but used a 205 cluster in a 204 and swapped out the speedo cluster had to pin the plugs since the wires came in at diffrent pin spots.
With my 165 I had to swap out temp gauges since I had one go bad on me and IIRC the meters in the gauges come apart similar to that of the 6th gen.
