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Failed emisions test

I recently purchased an 88 5kcstq. The car had failed emisions testing for the 
previous owner, so I did some minor repairs before making my first attempt. I 
replaced the spark plugs (bosch platinum 4), and the air filter. I also ran a 
couple of bottles of techron injector cleaner thorough it. The car still failed, 
but was better. It failed the hydrocarbons but past for CO (it previously 
failed both). I then replaced the cap, rotor and plug wires (ran much better, 
the wires were really bad) and the O2 sensor. The car ran so much better that I 
thought for sure it would pass, but it didn't. The weird thing is that it 
failed both CO and hydorcarbons this time.

What should I check next? I have checked all the hoses for vacuum leaks and 
they are all in really good shape. I am wondering about the WOT switch. I've 
read that this is a common part to fail and that it can do some funny things. I 
am also wondering if my injector seal are leaky (is there a good test for 

Overall the car runs, starts and idles very well. I only get 1.1 bar of boost 
(would love to get that up!). TIA.

John Uribe