[brucepick]

The load and throttle position sensor (TPS) numbers I've seen in my HX are basically same as yours. I have no Silverado experience to compare but it makes sense to me.

If you've seen those discussions of BSFC charts, the game for fuel efficiency is to have a small engine loaded kinda near max, not have a big engine choked off with high vacuum numbers.

First, load % is the pct of what the engine could do at that rpm, not vs flat out at red line rpm. At lower RPMs it can't suck in much air/fuel so by opening throttle even a bit, you soon let in almost as much air as it could possibly suck in. So TPS 30 or so will get you about 90% of max output (load) at about 2000-2200 rpm. OTOH, at 4000-6000 rpm it would be able to suck in so much air that TPS of 30-32 would actually limit it's output. So % load is reported as lower, for same TPS at higher RPMs.

About idle load figures. Similar logic but now you're down around 670 rpm. True, your foot is off the pedal so TPS is only 9 (on my car). However the idle air control holds the bypass valve partially open to maintain idle, so there is air flow even though TPS is closed (9). The approx 25% load you see is the result of that air flow vs what the tiny engine could do at that rpm if wide open. Apparently it calculates from air flow and not from throttle position.

Silverado has a much bigger engine, and likely has an idle speed that would provide more power at idle rpm, if wide open. At idle, it's probably running at higher vacuum (more air restriction) than your little civic engine. Just my guess though. Anyway, a 2x bigger engine running at an idle speed that is not half the Civic idle speed will show a smaller percent load at idle. But probably uses more fuel at idle than the Civic.