Issue after changing plugs?

[Rook2485]

So I recently bought an 89' S13 with a blacktop SR in it. I changed the plugs that were in it (NGK BKR8EIX iridiums) to the copper BKR7E. Both are gapped to .28, but with the new plugs it runs fine, but on WOT it only gets about 10psi when it's set to 16. Wasn't having this problem until I changed to the coppers. I'm going to pull the coppers out and double check the gap, but is my spark getting blown out? Do the iridiums HOLD a spark better?

Few mods- RS Empalthy ECU tune, Nismo 740cc injectors, S14 T28 turbo, Z32 MAF, stock ignition, stock intake manifold.

Thanks in advance.

[KaminaSan]

So I recently bought an 89' S13 with a blacktop SR in it. I changed the plugs that were in it (NGK BKR8EIX iridiums) to the copper BKR7E. Both are gapped to .28, but with the new plugs it runs fine, but on WOT it only gets about 10psi when it's set to 16. Wasn't having this problem until I changed to the coppers. I'm going to pull the coppers out and double check the gap, but is my spark getting blown out? Do the iridiums HOLD a spark better?

Few mods- RS Empalthy ECU tune, Nismo 740cc injectors, S14 T28 turbo, Z32 MAF, stock ignition, stock intake manifold.

Thanks in advance.

I'm also interested in finding this out, as my S14 BB turbo seems to only reach 5-6 psi until about 4500 rpm, then it hits 7 psi. The turbo spins fine. What could cause this?

I do have a low compression fully built engine, but didn't think it would affect it that much.

Did like 10 minutes of research:
Here are the possibilities, most of which I already knew.

1.)Bad Wastegate/Loose Wastegate
2.)Boost Leak
3.)Timing

[Rook2485]

So I put the plugs back in that were in there and it's still doing it. It pulled good once, but other than that every other time it was sluggish and only got to about 10 psi, until it got to almost redline then started to go up..