90 chevy 5.7L k1500 failed emissions

Other symptoms:
High idle has been a problem for a long time & ''service engine soon'' light has been coming on intermittantly for quite awhile (months).
Have changed oil & filter, o2 sensor, egr valve, throttle position sensor, cat converter, air filter, checked & fixed vacuum lines (this allowed me to clear error codes 32 & 44). While doing this work over a few weeks, engine rpm began surging except when under acceleration. Had diagnostic test done 2 days ago, which revealed the driver side fuel injector was bad. Replaced the injector, which cured the surging, but the ''service engine soon'' light still comes on, and there is still a high idle.
When I got the truck after the test, the service manager said I might have a vacuum leak at the TBI base plate gasket. I have not had time to check this.
Any input is welcome. Thank you...