98 taurus cylinder #1 misfire. Good spark, lifter? injector?

UPDATE: CEL stops flashing above 3300_rpm, then resumes flashing once engine rpms are decreased - same behavior under load or in neutral. Bank1 fuel trim is 10-15% at high rpms.

DESCRIPTION:
I'm trying to diagnose & fix a misfire on a 98 Ford Taurus. There's a good spark on cyl#1 (removing the spark plug cables gets a nice strong arc from about an inch away).

Cylinder#1 requires removing the manifold (I need new gaskets at a parts store, right?)

The car drives but bank1 trim is around 20% (bank2 trim is about 0%). Before the cyl #1 mis, the the bank1 trim was near 0.

Started yesterday after driving 400 miles straight. It's been intemitten for months and would self-clear after about 10-60 seconds and cause no issue or codes for days.

Should I replace injector #1, or do you think it's a stuck lifter?

Thank you.