98 Suburban Emissions Question

I have a 98 K2500 suburban with a 454 (54K miles) that won't pass the idle emissions test. It fails with a high hydrocarbon reading of 416, the test limit is 300.

The vehicle had a tune-up approximately 1,000 miles ago. A local shop ran a diagnostic test. Results indicated that the fuel pressure regulator was at fault.
I changed out the fuel pressure regulator and had the emission test done again. Results were the same as before.
The engine runs pretty smooth at idle, but will miss occasionally.
My first thought will be to look for vacuum leaks.
Any suggestions would be appreciated.
Thanks in advance.
Kevin
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I have a 98 K2500 suburban with a 454 (54K miles) that won't pass the idle emissions test. It fails with a high hydrocarbon reading of 416, the test limit is 300.
The vehicle had a tune-up approximately 1,000 miles ago. A local shop ran a diagnostic test. Results indicated that the fuel pressure regulator was at fault.
I changed out the fuel pressure regulator and had the emission test done again. Results were the same as before.
The engine runs pretty smooth at idle, but will miss occasionally.
My first thought will be to look for vacuum leaks.
Any suggestions would be appreciated.
Thanks in advance.
Kevin
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I think you should give it too me :-) I could use a CPI 454...
GMC Gremlin
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