You will probably see some gains, but not an over whelming amount of power unless you are going to go with over sized valves.

You could run the cam, and see what difference it makes, then open up the exhaust. Do to the age of the Runner a new exhaust may be do anyways.

What type of muffler are you running on your truck?

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed