What is the biblical argument against baptism by sprinkling/pouring? What is the biblical basis for the idea that it is wrong or incorrect to baptize by sprinkling or pouring the water? Growing up as a baptist I heard this all the time.

Related, but opposite: What is the biblical basis for baptism by sprinkling?
The argument from scripture centres firstly around the meaning of the original word which we translate as baptize in english:

Strong's Concordance
baptizó: to dip, sink
Original Word: βαπτίζω
Part of Speech: Verb
Transliteration: baptizó
Phonetic Spelling: (bap-tid'-zo)
Short Definition: I dip, submerge, baptize
Definition: lit: I dip, submerge, but specifically of ceremonial dipping; I baptize.
HELPS Word-studies
907 baptízō – properly, &quot;submerge&quot; (Souter); hence, baptize, to immerse (literally, &quot;dip under&quot;). 907 (baptízō) implies submersion (&quot;immersion&quot;), in contrast to 472 /antéxomai (&quot;sprinkle&quot;). - Biblehub.com (emphasis added)

It was the same word used to describe the dyeing process used at the time - cloth would be steeped (fully immersed) in dye.
Secondarily regarding what it signifies and what is therefore the most appropriate analogy:

3 Or don’t you know that all of us who were baptized into Christ Jesus were baptized into his death? 4 We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life. - Romans 6:3-4 NIV (emphasis added)

Baptism signifies our being buried with Christ - we have died to sin and our old life - and are raised to life new life in Him. Full immersion expresses this in a way that sprinkling does not.
Finally, there is no explicit biblical example of anyone being 'baptized' (using a wider  - ie. non-biblical - definition of the word) by sprinkling. You have to make up your mind whether to read implicit permission for sprinkling by synthesizing other scriptural doctrines, or reject it as a tradition from men.