Is a 90mm throttle body a direct bolt-on for my 2006 5.3?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

• 0411; 2007-2013: A three-bolt 78 mm cable throttle body can be fitted to a Gen IV four-bolt intake with an adapter, but that can choke an engine designed for a 90 mm throttle body; the better option is an aftermarket four-bolt cable-actuated body with TPS and IAC provisions, such as the 92 mm Nick Williams unit. (LSX Magazine (Power Automedia))
• 0411; 2007-2013: A 92 mm Nick Williams cable-actuated throttle body with TPS and IAC provisions is shown fitted to a four-bolt TBSS intake as the recommended cable-throttle option for Gen IV manifolds. (LSX Magazine (Power Automedia))
• E40; LS2; 2005-2006: The early Gen IV LS2 uses the E40 ECM with a completely redesigned four-bolt throttle body with a 90 mm silver blade; TAC functionality is integrated into the ECM, replacing the older P01 and P59 modules used in Gen III engines. (LSX Magazine (Power Automedia))
• E40; LS2; 2005-2006: The E40 ECM and the silver-blade LS2 throttle body can only work with each other; identify the E40 by its tall black connector plus short blue and gray connectors, versus the E67's short blue connector plus tall black and gray connectors. (LSX Magazine (Power Automedia))
• E92; L83, L86, LT1, LT4, LT5; 2014-2019: GM made three Gen V LT throttle body sizes: 80 mm for 5.3-liter trucks and SUVs, 87 mm for 6.2-liter trucks and sports cars like the Camaro and Corvette, and 95 mm exclusive to the supercharged LT5 in the 2019 C7 ZR1; each has its own mounting footprint, so swaps often require an adapter plate or a different intake manifold. (LSX Magazine (Power Automedia))
• LS2, LS3; 2007-2013: ICT Billet 551567 adapts a three-bolt 75 mm electronic (DBW) throttle body to a four-bolt intake (TBSS/LS2/LS3 manifolds), with a 102 mm intake port; it is for DBW bodies only, not mechanical cable bodies, and does not fit the LS4 intake. (Michigan Motorsports)
• ICT Billet 551513 adapts a three-bolt LS intake to a four-bolt throttle body, works with DBW or cable bodies, has a 75 mm through-hole tapering to 92 mm, and bodies above 92 mm need spacer 551517 plus longer bolts. (SD Parts)
• LS4; 2005-2009: ICT Billet 551560 adapts an LS4 intake to a three-bolt throttle body (DBW or cable), with a 75 mm opening. (SD Parts)
• E40; LS2; 2005-2006: GM 90 mm LS2 throttle body 12570790 is a four-bolt DBW unit for 2005-2006 LS2 Corvette, GTO, and Trailblazer; seller notes say the harness plug changed in 2007, implying 2005-2006 versus 2007+ wiring differences. (Jegs)

Confirm against the instructions for your exact parts before wiring. More: Throttle (drive-by-wire) in our tuning guide.