General Maintenance & Repairs - Need Help with 1994 Silverado

I have a 94 silverado with a 350 V8. Sometimes when I hit the gas the RPMS drop to about 100 or below for a second then kick back up. It stalls sometimes not verry often, and sometimes it take about 3 or 4 cranks to get it to start and it chuggs when it does start. Does anybody know what my problem could be.

The SES light is on and I had it read at AutoZone and it sent back two codes.

I thing the codes where: 42 and 43
but the lady at the store said it ment: Opti Spark EST Circuit grounded, and the oter was TPS out of Adjustment.

IDK if what the lady said was correct so I thought I would come here.

My first thought was TPS...throttle position sensor....I would buy one and install it to see if it fixes the problem, especially since it is throwing a code. You may also want to check your throttle body to make sure it is not sticking or anything when you hit/let off the gas....

I was going to say get some carb cleaner and clean out the throttle body.