Houston law technically requires:
Visual inspection (lights, emissions equipment)
Computer inspection (OBD-II diagnostics check)
Hardware inspection (horn, gas cap, etc)
Emissions inspection via sniffer (2wd cars or pre-OBDII cars)
Because our cars are AWD, we can bypass the sniffer - however you still need to pass visual inspection.
Determining if the inspection station actually cares or not, the will look for cats in the exhaust to make sure emissions equipment hasn't been tampered with. This is more luck of the draw - my full catless STi has passed inspection every time. My GF's catless STi failed visual inspection, but passed everything else. To get it to pass (you can re-inspect within 14 days at the same station for free) she had to put the stock downpipe back on.
Let me know if you got any more questions.