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Discussion Starter · #1 ·
I have two early '99 PowerStroke pickups.
#1 F250 Auto Transmission, 236xxx miles, no SES light or codes
#2 F350 Manual Transmission 130xxx miles, no SES light or codes

Both trucks have Ford AIS Intake, MBRP 4" Turbo back Exhaust with stock Catalytic Converters installed (required for emission test).
#2 has a PHP chip, but set on Stock and the readings haven't changed since before I added the chip.

Where I live requires annual emission checks. Every year, the trucks are +/- 1% of the previous year's results. They both pass easily, but for some reason, #1 has always been super clean and #2 always reads higher on its opacity results in spite of having about 1/2 the miles.

Here are this year's results:
#1 #2 (#*@! Can't seem to create columns. #1 is first column, #2 is second)
60 MPH 01% 12%
50 MPH 01% 16%
40 MPH 03% 19%

What could I check to find what is causing the higher emissions from my F350?

Thanks for your thoughts.
 

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Maybe #2 isn't broken in yet. :lookaround:

It could be something like a fuel pressure issue, ICP issue, maybe a difference in tuning. It would be interesting to do some testing, but I doubt the guy at the inspection station is going to let you play with his machinery while you change parameters.
 

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Boost leak?
 

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throw some cleaner in, maybe you the fuel system on the one truck is gummed up if it doesnt get driven as much as the other.

ya you could have a slight boost leak too
 
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