The PROBLEM actually came from the engine exaust, and your misreading your additives, they added something (cobolt?) as an additive to reduce the radar profile of their exhaust I think 3 fold.
The fact the russians could pick the aircraft up the moment it crossed the horizon with their airport radars just goes to show how useful all these stealth modifications really were.
But in it's defence, said radar profile was thanks to the high energy ionisd gas ejected from the engines that allowed a top speed of mach 3.5 in an era when they were facing mach 1.8 at the top end far closer to sea level, it was an excellent aircraft, although ungainly and poor manuverability.
Admittedly for the purpose it was built, spying on well defended targets, missile technology has far surpassed the airframe... although i wonder if the SR's theoretical successor, capable of mach 5, with improved cooling allowing mach 6 to 8 without damaging their aircraft... i wonder if we actually have a missile that could catch that from ground level in the modern inventory, aside from those insane anti-nukes lol.
But to be fair, I would nominate the XF-71 as the ultimate aircraft to ever be designed from those i have encountered... dropping gliding tactical nukes into the core of bomber fleets at mach 2.5 from an altitude that even modern fighters aren't built for.
And of course I eagerly anticipate it would be followed by the XB-71... a nuclear bomber that would make the russians wish they had improved their own (mach 5 nukes dropping in on your doorstep anyone?)
The biggest problem with the 71 series aside from the whole ionised gas component, was that even moderate turns at the speed they flew at led to high levels of Gforces, so they couldn't turn fast if they wanted to

Personally, if i could bring just one aircraft back, it'd be the 71... it has an ability to get and collect up to the second intelligence from anywhere in a matter of a few minutes, while satellites at best gives snapshots, a 71 could hang around for a few minutes giving electromagnetic intel, as well as video and the rest...
And best of all, you can time a satellite in orbit's arrival... a 71 could be there at any time ^_^
But the A-10 is the best combat aircraft for sure... but I feel that is mostly because some fool in congress used his connections to 'encourage' a alternate plan which was still in the design stage and ultimately got dropped for being incapable of meeting the requirements, which a 71 appears to have the capability to have met 'out of the box'.
The day the airforce failed to prevent the instructions to destroy the tooling required for this aircraft, is the day they failed at modern aviation.
And now the A-10?
What next, are they going to suggest we retire the M1 mbt?
And some people wonder why I hate politics, no matter who we vote in charge they make stupid and irrational decisions that either complicate our lives, cost us money, or generally ruin the few enjoyable bits of our lives we have left.