not sure what you have replaced yet but look into doing basics 1st, like plugs, fuel pump ect. Then get a better intercooler possibly
Speaking of "Stage 0", does anybody have a copy of those performance pages Dempsey Bowling made a while back? When he sold his turbovan a few months ago, those pages disappeared... If not, I'll have to write up some this summer...If I were you, I'd test the compression to see how the engine is doing. Then stage 0, which is tune up, wires, plugs, oil, coolant, transmission oil, etc, making the car runs like it suppose to first. Then, buy fuel pump and wideband sensor.
After all that, and $$$, I would start looking into upgrades.