High HC's when tested at 15 mph

My Van (1993 Astro engine code W 154,000 miles) is failing California's smog requirement.
They tested the van on rollers under load and found this:
HC's at 15 MPH (1475 RPM)
Allowed: 88 PPM max. The van got 164 PPM.
It passes in CO% and it passes for NOx (PPM) with flying colors and in the 25 MPH test it passes all three w/no problems... It runs clean at idle, and it runs clean at 2500 RPM (no load)
The van has never failed smog before and otherwise runs perfectly. This is the first time it's ever had to run on the rollers under load.
In an attempt to fix it I just replaced all the fuel injectors and the fuel pressure regulator. It now runs a bit cleaner:
It now fails w/109 PPM HC (down from 164. It's allowed 88)
The van has had a fairly recent tune-up that included a new pcv valve, ig. wires, plugs, rotors etc. cleaned the K&N filter etc. This was only about 10,000 miles ago.
Compression is good, starts right up, no CES codes, runs with about the same fuel economy as it ever has...
So basically it only belches out smog when I cruise around in a parking lot. What the heck do I do now?
Thanks,
Rayvan
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Rayvan wrote:

before an emissions test, I like to buy some Premium from more than one busy gas station, this way, I know the brew is true
Past experience has shown, stored cars need to burn off stale gas before taking test.
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talked into a new cat by a muffler guy the van's emissions dropped by about half and it had about half the mileage yours has. Also, the next time you have it tested, be sure to drive it on the freeway for 10 miles or so and leave it running while waiting for the test. Converters have to be hot to work efficiently.
HTH, WW
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