[mppickett]

I've only run a full bay intercooler on my turbo, but I ran both a water-air and water-meth injection on another car. I'm pretty handy and tried many different setups for water-air, but I was never really happy with the reliability or resistance to heat soak problems. I had very good results with water-meth injection.

All approaches have pros and cons. The water-meth is great for reducing the throttled air mass (improves responsiveness). Water-air is compact but the plumbing is complicated. Air-air has more throttled air mass than the other two (usually) but can be very effective with very little complexity.

If I was trying to keep the stock engine lid, I'd go for water-meth.