My first reaction to suddenly won't go more that 45mph is that the ALDA boost reference tube blew off.
As for the smoke I had a sudden NASCAR flashback(watching, not driving) of hole in the piston or burnt valve.

I'd do a tear down. Call it morbid curiosity, but I always like to know what went wrong and why. Maybe I can avoid it next time.

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I suggest we solve high gas prices with environmentalists... unfortunately they don't burn well.
1982 300CD, 220K miles: This vacuum system will be the death of me yet! (OBK #26)
1977 F150 400 C6 2wd, 10.2 sec 1/8 mile with 2.75 gears.
1965 Mustang. Mostly stock... LOL!
2001 Ram 2500, cummins, 5spd, 202k miles.(girlfriends)