My bad, it has been a while since I worked on this kind of car. The inline part you are talking about looks like a buffer, I would try leaving it out and connect the vacuum line directly to see if it makes a difference. Also, I would do a transmission service with a new filter. Here is a guide to help walk you through the steps:
https://www.2carpros.com/articles/how-to-service-an-automatic-transmission
1. Raise and support vehicle, then position drain pan under oil pan.
2. Remove front and side oil pan attaching bolts, then loosen rear pan attaching bolts.
3. Carefully pry oil pan loose from transaxle case and allow fluid to drain.
4. Remove remaining attaching bolt, oil pan and gasket. Thoroughly clean pan before reinstalling.
5. Remove and discard screen and O-ring seal.
6. Install replacement screen and O-ring seal, locating screen against dipstick stop.
7. Install gasket on oil pan, then apply Loctite 242 or equivalent to oil pan bolts to prevent leakage.
8. Torque oil pan bolts to 12-13 ft. lbs.
9. Lower vehicle and add approximately 6 qts. of fluid.
10. With selector in park, parking brake applied and engine at idle speed and operating temperature, check fluid level and add fluid as necessary. Do not race engine or move shift lever through ranges.
Bottom pan removal .................... 5.7L (6 qt.)
Complete overhaul .................... 7.6L (8 qt.)
Dry .................... 10.4L (11 qt.)
Please go over this guide and get back to us.
Monday, June 3rd, 2024 AT 10:03 AM