Changes that need to be made to accommodate the 20v by system
The complete 16v exhaust system can be used with the 20v silvertop. The only needed modification will be to the outermost flanges of the stock 16v header (pictures are of an ae86 header, but the bolt patern is the same)
The 20v header can also be used, but will require either a custom bpipe, or modifications to an existing 20v bpipe. The 20v silvertop header also has clearance issues with any exhaust side mounted starter. Clearance between the ST header and starter will only be a few millimeters.
The diameter of the 20v header pipes is identical to those on the 16v. The 20v header may have a slight advantage due to the use of theta plates, but dimensionally, the headers are the same or similar.
The 16v header can also be used with the blacktop, but will result in power loss due to the Blacktop’s larger exhaust ports. A typical 16v header/manifold will be a bit constricting. 16v manifolds have been used with blacktops, so it is possible. Larger diameter 16v headers may be available.
For best results, use the blacktop header (or exhaust header that has the same exhaust port dimensions) when possible.
The exhaust mounted starter will not clear the larger diameter blacktop header. This will be an issue with any 1985-1987.5 20v conversions where the original c50 transmission is to be used since these transmissions lack the intake side mounting position. You really have 3 options in this situation.
a. Use the 16v setup, and take the performance hit
b. Use a later c52 transmission (or bellhousing) that does have the intake starter mounting position
c. Modify the 20v header to clear the starter.
Once again, a custom bpipe will have to be made, or an existing bpipe modified
Keep in mind that 87+ mr2’s used a larger diameter bpipe, cat, and muffler, so this is your best choice for the 20v. The 4agze equipped mr2’s used the same exhaust setup as the NA cars did.