These are both very short chapters that mainly convey plot (that Bjornsen and Mickey G are close friends, and that Doc used to be a repo man).
Chapter 4 has this interesting passage:
Suddenly he was on some planet where the wind can blow two directions at once, bringing in fog from the ocean and sand from the desert at the same time, obliging the unwary driver to shift down the minute he entered this alien atmosphere, with daylight dimmed, visibility reduced to half a block, and all colors, including those of traffic signals, shifted radically elsewhere in the spectrum. (p.50)
Once again, Pynchon is describing an altered state of perception, this time the product of two elements that he has previously singled out (sand, in the references to the beach and the desert, and fog, or rather its polluted equivalent, smog). The aim here, as perhaps before, is to defamiliarise the setting, to highlight a loss of vision, certainly immediate, perhaps also on a grander scale (Doc here, as in Chapter 2, is driving whilst experiencing this).
The other point of interest is the ARPA, a forerunner of the Internet, which is described as looking like a ‘science fictional Christmas tree’ (p.53), which is a more positive image than the mention of precursors to search engines in Chapter 2, which should caution us not to confuse Pynchon with a technophobe.
There is also a not particularly subtle aside about the only weapon Doc carrying when he was a repo man was a truth serum that looked like a set of drug ‘works’. What is more interesting is that he never ended up using it.
It wasn’t long before he noticed how many of the delinquents he and Fritz visited seemed unable to keep their eyes off of it. He understood that if he was lucky, he might not have to so much as unzip it (p.52).
‘Lucky’ could be read as being ironic- that maybe it is not wholly fortunate to avoid the truth (though there are of course many good reasons why people work so hard at their denial). There is a fundamental dilemma in trying to analyse these kinds of passages, not just in Pynchon, but also in postmodern literature in general, which is that of tone. As Linda Hutcheon has pointed out, it is often difficult to know just how much of an ironical attitude we should assume on the part of the author. Sometimes this means we just have to read more carefully; at other times, all we have to go on are our preconceptions.