If it is a standard T34 the max would be 370 - 380 BHP, you will need Light Blue or Grey injectors. My view is that it is best to stay with standard cams but the head gasket should be changed to Cometic or better still O ring the block and fit the LATE Es Cos h/gasket (akaik) YB 1261 + chip and r/r session or live maping.

If you can fit a Hybrid T34 (360° bearing) then the limit is nearer to 400 - 420 BHP absolutely maximum! Then more or less the same spec as above BUT a ported head would now be worthwhile, you now need to fit GREY injectors and a 500 style inter cooler would also be a damn good idea!