1968 XR7 Engine Limit @ High Speed/RPM

Hello to all, I just got my 68 XR7 back from the shop. All is nearly well with the job they did. However, on the drive home, when I got up to speed 65 headed toward 70 MPH or about 2500-2600 RPM, it acted like it had a Rev limiter on it. It would bog down and get below say 60/2200 RPM and then could increase throttle. Those were my limits all the way home. When I got on the side streets I could accelerate and go beyond that RPM limit but it felt like I still was being restricted on speed and/or RPM. Any ideas? The shop is still researching this as well. Just had the fuel filter and fuel pump replaced.

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Any idea what the fuel pump pressure is? Stock fuel pump unrestricted against a flow restricted aftermarket carb might present peculiar issues. I have a regulator on mine to tame the stock pressure 12 psi +/- to 6.5 or <.

It’s fuel filter, fuel pressure low, sender sock plugged, or possible exhaust restriction…the fact that it revs to a higher rpm at lower speeds/gears indicates the fuel bowl is running empty

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What air cleaner does it have? Some foam cleaners have been known to collapse and block the airflow

My guess would be the filter sock in the tank is clogged. How old is the gas tank? When’s the last time the tank/sender unit has been touched/replaced?

I have seen a partially closed choke do restrict RPM on a few occasions. It’s just one more thing to check.

All are great thoughts. I will investigate each one. Thanks to all that responded. Have a Happy Thanksgiving!