hey i have a question about if i put a camshaft i need to modified something my engine is a 4K thanks

The engine of 4K has same kind Cam shaft like 5K and 7K

A week ago my friend has sell The TRD 70 for (4k 5k and 7K) 200 dollars.

He told me when he using the camshaft the idle is 2000-3000.Can peak until 9500 rpm.
The parts you must change together if you change cam,you have to change the spring valve (must be harder or you can add ring/coins if you kept the original spring valve 4K) and maybe tensioner of timing belt must be little modification.

If you don't change the spring valve,your engine will be floating in high rpm.But remember,too hard spring valve can broken your cam lobe.

So,you should to more consultation to the garage cause my English is not so good so i can't talk all about i know to you.i afraid my words make u mis under standing