[ QUOTE ]
What kind of boost does the van get? Can we just keep the wastegate close and expect the same boost level on a F250?
[/ QUOTE ]
Boost levels with a van turbo will probably drop a bit, but the turbo is operating more efficiently, so your power should actually go up, even with less boost.
Keeping the wastegate closed on the PU turbo will net higher boost numbers due to the smaller exhaust housing, but that's not always good. At boost levels above 25 psi or so (I beleve it's 25 psi), you have moved out of the map of the compressor wheel and you are beginning to superheat the air. More boost does make more power, but hotter makes less power. And, in the case of the stock turbo at elevated boost levels, that heat loses more power than the increased boost gains.