Need help making the decision on 22RE engine swap

Hello,
I really need help on this.

Here is a little story.

I owned a 1990 toyota 4x4 pickup truck. It has a reliable 22RE engine with 187k miles on it. The truck is running weak. I have to switch to the 4th gear if going up a little hill/curve, even while driving on the freeway.

So, I took it to the mechanic to have the valves adjusted, but that didn't help. Then my mechanic inspected the timing chain and said the timing chain is loosing & that causes the truck to loose horse power. He suggested to replace the timing chain to regain the horse power. He wants $800 for parts and labor.

Anyway, here is my question/concern:
1) Do you think what the mechanic said is true? I don't want to spend $800 replacing the timing chain and the truck still drives weak.

2) If spending $800 on the timing chain, do you think I'd better replace the engine with a rebuilt 22RE?

Thanks for all your help

I'd make sure it wasn't just a clogged cat conv first. Loss of power uphill is a symptom of that also.

When was the TC last replaced? They're good for 100K mi.
You can check yourself for slack. Just pull the valve cover, the TC will be sitting right there in front. Pull on it, a 1/4 to1/2 inch of play is normal.
If it is stretched to much it can wear a hole in the TC Cover (then you have oil and coolant mixing, not good), or it could jump a tooth and you'll really loose power, or if it breaks you can have major engine damage.

If you do have it replaced, a competent mechanic will suggest having the water pump replaced also, and maybe the belts and hoses if they're old.

Thanks fourwd1 - AF Advisor.
I just checked the timing chain as you suggested. Yes, it is loosing more than 1/2". I pushed the chain toward the other side of the chain and it moved almost half way.
I'll bring it to the shop for TC replacement this week.

Thanks for your help.

update:
I just had the timing chain and water pump replaced this weekend. The truck seems to gain a little more power.
Thanks